AnaGram interim repo (temporary): doc/manual/sf.tex annotate

annotate doc/manual/sf.tex @ 21:1c9dac05d040

Add lint-style FALLTHROUGH annotations to fallthrough cases. (in the parse engine and thus the output code) Document this, because the old output causes warnings with gcc10.

author	David A. Holland
date	Mon, 13 Jun 2022 00:04:38 -0400
parents	13d2b8934445
children

rev	line source
0 13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1 \chapter{Syntax Files}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	2 \index{Syntax file}\index{File}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	3
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	4 Input files to AnaGram are called \agterm{syntax files}. A syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	5 file comprises a grammar and associated C or C++ code. The grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	6 consists of a number of productions along with supportng information
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	7 such as configuration sections and definitions of character sets. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	8 associated code consists of reduction procedures (see \S 8.2.13) and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	9 embedded C or C++ code (\S 8.2.17). This chapter explains the rules
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	10 for writing syntax files acceptable to AnaGram. The rules for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	11 interfacing your parser to the balance of your program are given in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	12 Chapter 9.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	13
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	14
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	15 \section{Lexical Conventions}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	16 \index{Lexical conventions}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	17
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	18 \subsection{Statements}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	19 \index{Statements}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	20
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	21 For purposes of this manual, AnaGram statements are considered to be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	22 productions, definition statements, configuration sections, and blocks
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	23 of embedded C or C++ code, all discussed individually below. Each
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	24 statement must begin on a new line. It is a good idea to separate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	25 statements visually in your file by using blank lines freely.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	26 There are generally no restrictions on the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	27 \index{Statements}\index{Order of statements}order of statements
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	28 in a syntax file. Good programming practice, however, suggests that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	29 definitions and configuration sections should precede the grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	30 itself.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	31
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	32 \subsection{Spaces and Tabs}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	33 \index{Spaces}\index{Tabs}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	34
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	35 AnaGram allows spaces and tabs to be used freely to improve the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	36 readability of grammars. Spaces and tabs are ignored, except when
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	37 embedded in a token name, in a character set definition, or in a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	38 keyword. Within a token name, any sequence of spaces and tabs counts
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	39 as a single space.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	40
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	41 \subsection{Continuation Lines}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	42 \index{Continuation lines}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	43
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	44 AnaGram statements normally end with a newline character or the end of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	45 file. If AnaGram encounters the end of a line and the statement it is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	46 reading appears to be complete, it will not look for a continuation.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	47 To continue a statement to another line, just make sure that what you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	48 have on the first line is clearly incomplete. For example,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	49
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	50 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	51 prep phrase -> preposition, "the", noun
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	52 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	53
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	54 looks complete to AnaGram, whereas
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	55
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	56 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	57 prep phrase -> preposition, "the", noun,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	58 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	59
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	60 looks incomplete because of the dangling comma at the end.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	61
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	62 \subsection{Comments}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	63 \index{Comments}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	64
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	65 AnaGram accepts comments in accordance with the rules of C and C++,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	66 that is, normal C comments bracketed with \agcode{/} and \agcode{/},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	67 as well as comments which begin with \agcode{//} and continue to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	68 end of line. AnaGram also observes these conventions when skipping
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	69 over embedded C code.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	70
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	71 Since the ANSI standard for C insists that normal C comments do not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	72 nest, AnaGram, by default, disallows nested comments. You may,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	73 however, set a configuration parameter,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	74 \index{Nest comments}\index{Configuration switches}\index{Comments}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	75 \agparam{nest comments},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	76 to allow nested comments. See Appendix A. In any case, AnaGram will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	77 use the same convention for embedded C as it uses for AnaGram proper.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	78 You can change the convention in the middle of the file if necessary.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	79
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	80 AnaGram treats each comment delimited with \agcode{/} and \agcode{/}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	81 as though it were a single space. You can even put such comments in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	82 the middle of token names if you should want to. A comment that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	83 begins with \agcode{//} is treated as though the end of line occurred
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	84 at the \agcode{//}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	85
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	86 \subsection{Blank Lines and Form Feeds}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	87 \index{Blank lines}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	88
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	89 Because blank lines and form feeds are visual separators, AnaGram will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	90 not skip either looking for a continuation line. Therefore blank lines
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	91 and form feeds can occur only between AnaGram statements, not in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	92 middle of a statement.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	93
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	94 It is a good idea to separate groups of productions with a blank line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	95 or two, lest an accidental dangling comma make AnaGram think the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	96 beginning of the next production is a continuation of the present one.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	97
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	98
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	99 \section{Elements of Grammars}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	100
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	101 \subsection{Names}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	102 \index{Name}\index{Token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	103
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	104 You may use names to represent tokens, character sets, keywords and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	105 \index{Virtual productions}\index{Production}virtual productions.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	106 Names follow the same general rules as for any programming language,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	107 with the notable exception that they may have embedded white space.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	108 Names are made up of letters, digits, or underscores. They may not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	109 begin with a digit. Any sequence of embedded spaces, tabs or comments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	110 counts as a single space. AnaGram distinguishes between upper and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	111 lower case\index{Case sensitivity}, so that \agcode{Word} and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	112 \agcode{word} are different names. There is no particular limit to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	113 length of a name. There are no reserved words as such, although
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	114 \agcode{grammar}, \agcode{eof}, and \agcode{error} will be treated as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	115 reserved words unless you take special action by setting appropriate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	116 configuration parameters. The names AnaGram uses for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	117 \index{Configuration parameters}configuration parameters
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	118 follow the same rules as for other names, except that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	119 \index{Case sensitivity}case
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	120 is ignored.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	121
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	122 \subsection{Reserved Words}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	123 \index{Reserved words}\index{Words}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	124
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	125 % XXX shouldn't that be \index{Grammar token}?
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	126 AnaGram treats tokens with the names \index{Grammar}\agcode{grammar},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	127 \index{Eof token}\index{Token}\agcode{eof}, and \index{Error
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	128 token}\index{Token}\agcode{error} in a special manner unless certain
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	129 measures are taken. Since you can override AnaGram's use of these
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	130 names, they are not reserved words in the true sense.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	131
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	132 If your grammar has a token named \agcode{grammar}, AnaGram will take
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	133 that token to be the grammar token for your grammar unless you set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	134 \index{Token}\index{Grammar token}\index{Configuration parameters}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	135 \agparam{grammar token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	136 configuration parameter or mark some other token as the grammar token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	137 using ``\index{ \_dol}\$''.% See below ???.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	138
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	139 If your grammar has a token named \agcode{error} and you take no
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	140 further steps, AnaGram will assume you wish to use error token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	141 resynchronization in case of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	142 \index{Syntax error}\index{Errors}syntax error. See Chapter 9.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	143 If you wish to use some other token as an error token you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	144 may select it using the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	145 \index{Configuration parameters}\index{Token}\index{Error token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	146 \agparam{error token} configuration parameter.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	147 If you wish to use \agcode{error} as a token name, but do not want
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	148 error token resynchronization, you may set the \agparam{error token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	149 configuration parameter to any name that is not used in your grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	150 You may then use \agcode{error} as a token name without causing
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	151 AnaGram to include error token resynchronization in your parser.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	152
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	153 \index{Resynchronization}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	154 If you select automatic resynchronization or error token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	155 resynchronization (see Chapter 9), AnaGram will look for a token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	156 called \agcode{eof} to use as an end of file indicator. You may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	157 either name your end of file token \agcode{eof} or you may set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	158 \agparam{eof token} configuration parameter with the name of your end
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	159 of file token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	160
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	161 \subsection{Variable Names}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	162 \index{Name}\index{C variable names}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	163
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	164 With AnaGram you can associate C/C++ variable names with the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	165 \index{Semantic value}\index{Token}\index{Value}semantic values of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	166 tokens for use in your \index{Reduction procedure}reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	167 procedures. Each name follows the corresponding token in the grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	168 rule on the right of the production, separated from the token by a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	169 colon. AnaGram allows variable names made up of letters, digits, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	170 underscores. They may not begin with a digit. Embedded spaces, tabs
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	171 or comments, are not allowed, of course. AnaGram imposes no
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	172 restriction on length, but uses your variable names just as you have
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	173 written them in the code it generates to call reduction procedures.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	174 Remember that your compiler may have a limit on the length of variable
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	175 names. Also, AnaGram itself uses C variable names beginning with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	176 \agcode{ag{\us}}. It is therefore wise to avoid using names of this form.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	177
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	178 \subsection{Terminal Tokens}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	179 \index{Terminal token}\index{Token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	180
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	181 A \agterm{terminal token} is a token which does not appear on the left
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	182 side of a production. It represents, therefore, a basic unit of input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	183 to your parser. You have several options with respect to terminal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	184 tokens. If the input to your parser consists of ASCII characters, you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	185 may define terminal tokens explicitly as ASCII characters or as sets
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	186 of ASCII characters. If you have an input procedure which produces
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	187 numeric codes, you may define the terminal tokens directly in terms of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	188 these numeric codes. On the other hand, you may leave the terminal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	189 tokens completely undefined. In this case, you must provide an input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	190 procedure which can determine the appropriate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	191 \index{Token}\index{Token number}\index{Number}token numbers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	192 It is an all or none situation. If you provide any explicit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	193 definitions, you must provide them for all terminal tokens. Input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	194 procedures and token input are discussed in Chapter 9. Examples of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	195 non-character input may be found in the Macro Preprocessor example in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	196 the \agfile{examples/mpp} directory on your AnaGram distribution
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	197 disk.% Further examples are given in Chapter ???.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	198 % XXX change ``on ...distribution disk'' to ``in ...distribution''.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	199
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	200 \subsection{Character Representations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	201 \index{Character representations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	202
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	203 In specifying admissible input characters you may use \index{Character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	204 constants}character constants following the normal C conventions.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	205 Remember that a character constant may specify only a single
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	206 character. Although some C compilers will allow constructs such as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	207 \agcode{'mv'}, AnaGram doesn't allow this. AnaGram recognizes the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	208 same escape sequences as C, including octal and hex sequences, even
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	209 though this is, strictly speaking, unnecessary. The escape sequences
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	210 AnaGram recognizes are:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	211
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	212 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	213 % It would be nice to be able to just write this and tell latex to set
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	214 % it in three columns. but no... that would be too easy.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	215 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	216 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	217 %\begin{tabular}{ll}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	218 %\agcode{{\bs}a}&alert (bell) character\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	219 %\agcode{{\bs}b}&backspace\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	220 %\agcode{{\bs}f}&formfeed\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	221 %\agcode{{\bs}n}&newline\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	222 %\agcode{{\bs}r}&carriage return\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	223 %\agcode{{\bs}t}&horizontal tab\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	224 %\agcode{{\bs}v}&vertical tab\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	225 %\agcode{{\bs\bs}}&backslash\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	226 %\agcode{{\bs}?}&question mark\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	227 %\agcode{{\bs}'}&single quote\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	228 %\agcode{{\bs}"}&double quote\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	229 %\agcode{{\bs}ooo}&octal number\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	230 %\agcode{{\bs}xhh}&hexadecimal number\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	231 %\end{tabular}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	232
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	233 \begin{indenting}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	234 \begin{tabular}{llllll}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	235 \agcode{{\bs}a}&alert (bell) character&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	236 \agcode{{\bs}t}&horizontal tab&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	237 \agcode{{\bs}'}&single quote\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	238 \agcode{{\bs}b}&backspace&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	239 \agcode{{\bs}v}&vertical tab&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	240 \agcode{{\bs}"}&double quote\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	241 \agcode{{\bs}f}&formfeed&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	242 \agcode{{\bs\bs}}&backslash&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	243 \agcode{{\bs}\textit{ooo}}&octal number\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	244 \agcode{{\bs}n}&newline&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	245 \agcode{{\bs}?}&question mark&
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	246 \agcode{{\bs}x\textit{hh}}&hexadecimal number\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	247 \agcode{{\bs}r}&carriage return\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	248 \end{tabular}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	249 \end{indenting}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	250 \bigskip
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	251
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	252 The octal escape sequence allows up to three octal digits, in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	253 accordance with ANSI specifications for C. The hexadecimal numbers
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	254 may contain an arbitrary number of digits; however AnaGram will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	255 truncate the result to sixteen bits.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	256
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	257 A backslash followed by any character other than those listed above
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	258 will cause a syntax error.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	259
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	260 You may also represent characters by writing the numeric code
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	261 explicitly, in decimal, octal, or hexadecimal representations.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	262 AnaGram follows the C conventions for integer constants: a leading
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	263 \agcode{0} means the number is octal, a leading \agcode{0x} or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	264 \agcode{0X} means it is hexadecimal. The hex digits \agcode{a-f} may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	265 be either upper or lower case\index{Case sensitivity}. Numbers may be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	266 preceded by an optional minus sign.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	267
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	268 If your parser uses a pre-existing \index{Lexical scanner}lexical
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	269 scanner and you wish to use the code numbers it generates to identify
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	270 tokens, you may simply treat those code numbers as character numbers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	271 You may use the numbers directly in your productions, or you may use
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	272 definition statements to name them. You may also use an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	273 \agparam{enum} statement within a configuration section to attach
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	274 names to the code numbers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	275 % XXX shouldn't this use of enum be indexed?
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	276
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	277 AnaGram also allows a special notation for control characters. You
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	278 may represent a control character by using the ``\^{}'' character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	279 preceding any printing ascii character. Thus you can write
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	280 \agcode{\^{}z} or \agcode{\^{}Z} to represent the DOS end-of-file
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	281 character. Notice that quotation marks are not necessary.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	282
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	283 Examples of character representations:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	284
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	285 \begin{indenting}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	286 \begin{tabular}{cccc}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	287 \agcode{'K'}&\agcode{-1}&\agcode{0}&\agcode{'{\bs}t'}\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	288 \agcode{\^{}J}&\agcode{'{\bs}xff'}&\agcode{077}&\agcode{0XF3}\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	289 \end{tabular}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	290 \end{indenting}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	291
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	292 \subsection{Character Ranges}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	293 \index{Character range}\index{Range}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	294
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	295 It is convenient to be able to specify ranges of characters when
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	296 writing a grammar. AnaGram supports several ways of representing
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	297 ranges of characters. The first is an extension of the notation for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	298 character constants: \agcode{'a-z'} is the set of lower case
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	299 characters. You can even use escape sequences such as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	300 \agcode{'{\bs}n-{\bs}r'} if you like. The order of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	301 characters used to specify the range is immaterial: \agcode{'z-a'} is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	302 the same as \agcode{'a-z'}. AnaGram will, however, issue a warning
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	303 just in case the unusual order results from a clerical error.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	304
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	305 The second way to specify a range is by using two arbitrary character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	306 representations, as described above, separated by two dots. For
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	307 example, \agcode{\^{}C..\^{}Z}, \agcode{3..26}, \agcode{3..032},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	308 \agcode{3..0x1a}, and \agcode{\^{}C..0x1a}, all represent the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	309 range of characters. Similarly, \agcode{'A-F'}, \agcode{'A'..'F'},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	310 \agcode{0101..0106}, \agcode{0x41..0x46}, \agcode{65..70}, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	311 \agcode{65..'F'} all represent the same range of characters.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	312
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	313 \subsection{Character Sets}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	314 \index{Character sets}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	315
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	316 If you provide explicit definitions for terminal tokens, the basic
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	317 input unit for your parser will be considered a character set, even if
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	318 your input procedure provides numeric codes that are not actually
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	319 characters. As a terminal token, a character set will be matched by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	320 any input character that is a member of the set. Character sets may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	321 be named in definition statements, but they may also appear on the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	322 right sides of productions without being named.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	323
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	324 A character set may consist of one or more characters. You can
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	325 specify a character set that consists of a single character by using
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	326 any of the character representation methods described above. You can
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	327 specify a set consisting of a range of characters by using any of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	328 representations of character ranges described above.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	329 \index{Character sets}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	330 To specify more complicated sets, you can write
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	331 \index{Expressions}\index{Set expressions}expressions
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	332 using conventional set theoretic operations.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	333 In AnaGram input, these operations are specified as follows:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	334
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	335 \index{Union}\index{Difference}\index{Intersection}\index{Complement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	336 \begin{indenting}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	337 \begin{tabular}{cl}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	338 \agcode{A + B}&(union)\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	339 \agcode{A - B}&(difference)\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	340 \agcode{A \& B}&(intersection)\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	341 \agcode{\~{}A}&(complement)\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	342 \end{tabular}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	343 \end{indenting}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	344
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	345 where \agcode{A} and \agcode{B} are arbitrary sets. Union and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	346 difference have the same precedence. Intersection has higher
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	347 precedence and complement has the highest precedence. Thus in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	348 expression
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	349
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	350 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	351 A + \~{}B\&C
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	352 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	353
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	354 the complement operation is performed first, then the intersection,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	355 and finally the union.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	356
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	357 Watch out! In an AnaGram syntax file \agcode{65 + 97} represents the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	358 character set which consists of lower case \agcode{a} and upper case
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	359 \agcode{A}. It does not represent 162, the sum of 65 and 97.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	360
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	361 Parentheses may be used to force the order of evaluation:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	362
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	363 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	364 \~{}(A \& (B+C))
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	365 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	366
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	367 In this example the union of \agcode{B} and \agcode{C} is calculated,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	368 then the intersection of this set with \agcode{A} is calculated, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	369 finally the complement is evaluated.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	370
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	371 The computation of the \index{Complement}complement of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	372 \index{Character sets}set requires a definition of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	373 \index{Universe}universe of set elements. AnaGram will define the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	374 universe to be the set of unsigned 8-bit characters, unless one or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	375 more characters outside that range have been specified. In that case,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	376 the universe will consist of all characters on the interval defined by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	377 the lesser of zero and the lowest character code used and the greater
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	378 of 255 and the highest character code used. The complement of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	379 character set is everything in this universe except the characters in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	380 the set.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	381
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	382 Characters which make up part of the character universe, but are not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	383 legitimate input according to your grammar, are lumped together into a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	384 special token which will cause an error if it occurs in your input.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	385
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	386 When your parser reads an input character, it uses that character to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	387 index a conversion table in order to determine the appropriate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	388 \index{Token number}\index{Token}\index{Number}token number. If the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	389 \index{Range}\index{Test range}\index{Configuration switches}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	390 \agparam{test range} configuration switch
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	391 is on, its default setting, your parser will include code to verify
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	392 that the character is in bounds before it indexes the conversion
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	393 table. If you are satisfied that checking bounds is unnecessary, you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	394 may turn the \agparam{test range} switch off and get a slightly higher
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	395 level of performance from your parser.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	396
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	397 For efficient processing, it is well to keep the number of tokens to a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	398 minimum. Therefore if you have a choice between defining a construct
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	399 as a token, with a production, or a set, with a definition, the set is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	400 to be preferred.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	401
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	402 Some useful character sets are:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	403
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	404 \begin{indenting}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	405 \begin{tabular}{ll}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	406 \agcode{'a-z' + 'A-Z'}&Alphabetic characters\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	407 \agcode{'a-f' + 'A-F'}&Hex digits\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	408 \agcode{'0-9'}&Decimal digits\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	409 \agcode{0..127}&ASCII character set\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	410 \agcode{32..126}&Printing ASCII characters\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	411 \agcode{\~{}'{\bs}n'}&Anything but newline\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	412 \agcode{\^{}Z}&Windows/DOS end of file indicator\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	413 \agcode{-1}&Stream I/O end of file indicator\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	414 \agcode{0}&String terminator\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	415 \agcode{32..126 - 'a-z' - 'A-Z' - '0-9'}&Punctuation\\
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	416 \end{tabular}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	417 \end{indenting}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	418 \bigskip
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	419 % XXX ``punctuation'' is wrong; it should subtract off space too
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	420
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	421 Note that \agcode{'a-z'} is a range of characters but
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	422 \agcode{32..126 - 'a-z'} is a set difference.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	423
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	424 When AnaGram encounters a character set in a grammar rule, it assigns
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	425 a token number to the character set. If it has previously seen the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	426 same character set it will assign the same token number; however, it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	427 assigns the same token number only if the set expressions are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	428 obviously the same. Thus, AnaGram will assign the same token number
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	429 every time it sees \agcode{A + B}, but will assign a different token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	430 number if it sees \agcode{B + A}. Only when AnaGram has finished
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	431 scanning the entire syntax file can it actually evaluate the character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	432 sets. If it finds that several different tokens all refer to the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	433 character set, it will create a single token that represents the true
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	434 character set and create
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	435 \index{Shell productions}\index{Production}``shell productions'' for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	436 the others.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	437
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	438 \index{Character sets}If the character sets you use in your grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	439 overlap, they do not properly represent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	440 \index{Terminal token}\index{Token}terminal tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	441 To deal with this situation, AnaGram identifies all overlaps among
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	442 character sets and extends your grammar by adding a number of extra
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	443 productions. For instance, suppose your grammar uses the following
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	444 character sets as though they were terminal tokens:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	445
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	446 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	447 'a-z' + 'A-Z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	448 '0-9'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	449 '0-7'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	450 'a-f' + 'A-F'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	451 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	452
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	453 AnaGram will then modify your grammar by adding the following productions:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	454
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	455 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	456 'a-z' + 'A-Z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	457 -> 'a-f' + 'A-F' \| 'g-z' + 'G-Z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	458
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	459 '0-9'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	460 -> '0-7' + '8-9'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	461 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	462
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	463 Although the tokens \agcode{'a-z' + 'A-Z'} and \agcode{'0-9'} are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	464 technically now
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	465 \index{Nonterminal token}\index{Token}nonterminal tokens,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	466 for purposes of determining the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	467 \index{Token}\index{Data type}data type of their
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	468 \index{Semantic value}\index{token}\index{Value}semantic values,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	469 AnaGram continues to regard them as terminal tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	470
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	471 This \index{Partition}\index{Universe}\index{Character universe}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	472 ``partitioning'' of the character universe is described in Chapter 6.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	473
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	474 \subsection{Keyword Strings}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	475 \index{Keywords}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	476
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	477 In your grammar, AnaGram recognizes character strings within double
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	478 quotes (e.g., \agcode{"IF"}) as keywords. The strings follow the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	479 syntactic rules as strings in C. The same escape sequences are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	480 honored. AnaGram does not, however, allow for the concatenation of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	481 adjacent strings. Note that AnaGram strings are used only for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	482 definition of keywords in your grammar, not for messages to be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	483 displayed or printed.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	484
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	485 Keyword strings may not include null characters and must be at least
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	486 one character long. You may have any number of keywords. Each is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	487 treated as a single terminal token. A keyword may be given a name by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	488 means of a definition statement. Keywords may appear in virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	489 productions.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	490
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	491 AnaGram's keyword recognition works in the following way. First, for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	492 each state in your parser, AnaGram prepares a list of all the keywords
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	493 that are admissible in that state. Your parser will recognize a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	494 keyword \emph{only} if it is in an appropriate state; otherwise it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	495 will appear to be an anonymous sequence of characters. Your parser,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	496 in any state, checks for keywords it expects before it checks for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	497 acceptable characters. That is, \emph{keywords take precedence} over
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	498 simple characters. It does not look for keywords that would not be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	499 acceptable input. The parser will do whatever lookahead is necessary
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	500 in order to pick up the entire keyword. Thus if the character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	501 \agcode{I} and the keyword \agcode{IF} are both legitimate input at
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	502 some point, \agcode{IF} will be recognized, if present, in preference
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	503 to \agcode{I}. If several admissible keywords match the input, such
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	504 as \agcode{IF} and \agcode{IFF}, the parser will select the longest
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	505 match, \agcode{IFF} in this example.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	506
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	507 AnaGram does not incorporate keywords into its character sets.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	508 Keywords stand apart and should not appear in definitions of character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	509 sets. In particular, they are not considered as belonging to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	510 complement of a character set. Thus for the production
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	511
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	512 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	513 next char -> \~{}('{\bs}n' + \^{}Z)
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	514 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	515 a keyword would not be considered legitimate input.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	516
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	517 Note also that a keyword consisting of a single character does not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	518 belong to the character universe. Because of this fact, AnaGram's
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	519 treatment of \agcode{'X'} and \agcode{"X"} is very different. If this
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	520 seems confusing at first, try using only keywords which are at least
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	521 two characters long until you have some experience with them.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	522
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	523 AnaGram's keyword recognition logic normally does not make any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	524 assumptions about what precedes or follows a keyword. Thus if
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	525 \agcode{int} is a keyword, your parser will be capable of plucking it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	526 out of a string of characters such as \agcode{disintegrate} if,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	527 according to your grammar, it could follow \agcode{dis}. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	528 \agparam{sticky} declaration and the \agparam{distinguish keywords}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	529 statement, described below, can prevent such unwanted recognition of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	530 keywords. A keyword following a \agparam{sticky} token will not be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	531 recognized if the first character of the keyword can be shifted in as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	532 part of the \agparam{sticky} token. The \agparam{distinguish
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	533 keywords} statement prevents recognition of a keyword if it is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	534 followed immediately by a character of the sort that makes up the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	535 keyword.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	536
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	537 \subsection{Type Specifications For Tokens}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	538 \index{Token}\index{Token type}\index{Type declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	539
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	540 When you write productions or token declarations (see below), AnaGram
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	541 allows you to specify the data type\index{Token}\index{Data type} of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	542 the \index{Semantic value}\index{Token}\index{Value}semantic value of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	543 a token by using a C or C++ data type specification. The restrictions
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	544 are that AnaGram does not allow specification of array or function
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	545 types, nor explicit structure types. Types that are defined with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	546 typedef statements, structure definitions, or class definitions,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	547 including template classes, in your embedded C or C++ are acceptable.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	548 Thus the following specifications, for example, are acceptable:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	549
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	550 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	551 void
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	552 int
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	553 char *
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	554 unsigned long *near
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	555 static float *far
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	556 my{\us}type
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	557 double *
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	558 struct descriptor
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	559 struct widget *
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	560 vector <double> *
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	561 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	562
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	563 On the other hand, the following specifications are \emph{not} valid:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	564
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	565 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	566 int[20]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	567 int *(int, unsigned char)
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	568 \bra int x,y; float z; \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	569 struct \bra int k; float z; \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	570 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	571
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	572 Note that AnaGram itself does nothing with the type specifications. It
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	573 simply passes them on to your compiler as appropriate.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	574
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	575 \subsection{Productions}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	576 \index{Production}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	577
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	578 Productions are the basic units of a grammar. A production consists
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	579 of a left side and a right side. \index{Left side}The left side of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	580 production consists of one or more token names, joined by commas,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	581 optionally preceded by a type specification enclosed in parentheses.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	582 \index{Right side}The right side begins with an arrow and may either
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	583 begin on the same line as the left side or on a new line. For
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	584 example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	585
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	586 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	587 program -> statement list, eof
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	588 expression
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	589 -> expression, plus, term
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	590
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	591 (int) variable name, function name
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	592 -> name:n = look{\us}up(n);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	593 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	594
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	595 The part of the right side of a production following the arrow is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	596 called a \index{Grammar rule}\index{Rule}\agterm{grammar rule},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	597 discussed below. A production need not have a right side at all. In
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	598 this case, it is simply called a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	599 \index{Declaration}\index{Token}\agterm{token declaration}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	600 AnaGram assigns
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	601 \index{Token number}\index{Token}\index{Number}token numbers
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	602 to the token names on the left side, and, if there is a type
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	603 specification, records the data type for each of the tokens declared.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	604 Declarations of this sort are most useful when using input from a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	605 \index{Lexical scanner}lexical scanner. See Chapter 9 for a discussion
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	606 of techniques for interfacing a lexical scanner to your parser. If
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	607 you do not intend to use a lexical scanner you will have no need for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	608 token declarations.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	609
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	610 If you do not explicitly specify the type for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	611 \index{Semantic value}\index{Token}\index{Value}semantic value
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	612 of a token, it will be determined by the configuration parameter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	613 \index{Default token type}\index{Configuration parameters}\index{Token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	614 \agparam{default token type}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	615 if it is a \index{Nonterminal token}\index{Token}nonterminal token or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	616 by the \index{Configuration parameters}configuration parameter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	617 \index{Input token type}\index{Default input type}\agparam{default input type}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	618 if it is a \index{Token}terminal token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	619 \agparam{Default token type} defaults to \agcode{void}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	620 \agparam{Default input type} defaults to \agcode{int}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	621
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	622 If a production has more than one token on the left side, as in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	623 third example above, it is called a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	624 \index{Semantically determined production}\index{Production}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	625 \agterm{semantically determined production}. Semantically determined
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	626 productions are a useful tool for exerting semantic control over
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	627 syntactic analysis. A semantically determined production should have
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	628 a reduction procedure which determines on a case by case basis which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	629 of the tokens on the left side should be taken as the reduction token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	630 If there is no reduction procedure, or if the reduction procedure does
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	631 not make a choice, the reduction token will be the first syntactically
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	632 correct token on the left side of the production. In the example
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	633 above, \agcode{variable name} will be the reduction token unless
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	634 \agcode{look{\us}up} changes it to \agcode{function name}. Semantically
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	635 determined productions are discussed more fully in Chapter 9.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	636
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	637 If several productions have the same left side, it does not need to be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	638 repeated. Subsequent right hand sides must each start on a new
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	639 line. For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	640
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	641 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	642 integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	643 -> digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	644 -> integer, digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	645
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	646 name
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	647 -> letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	648 -> name, letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	649 -> name, digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	650 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	651
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	652 On the other hand, you do not have to group productions with the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	653 left side. You could write the above productions as follows, although
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	654 it would certainly not be good programming practice:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	655
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	656 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	657 name -> name, digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	658 integer -> integer, digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	659 name -> name, letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	660 integer -> digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	661 name -> letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	662 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	663
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	664 Nevertheless, there are a few occasions involving complex cross
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	665 recursions and semantically determined productions where it is not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	666 possible to group productions neatly.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	667
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	668 The right side of a production can be empty. Such a production is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	669 called a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	670 \index{Null productions}\index{Production}\agterm{null production}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	671 Null productions are useful to denote an optional element in a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	672 grammar, or a list that may be empty. For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	673
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	674 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	675 optional widget
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	676 ->
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	677 -> widget
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	678
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	679 optional qualifiers
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	680 ->
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	681 -> optional qualifiers, qualifier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	682 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	683
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	684 A second way to write multiple productions with the same left side
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	685 uses the \index{Vertical bar}\index{\|}vertical bar character, ``$\|$'',
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	686 to separate the grammar rules. The productions given above for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	687 \agcode{name}, \agcode{optional widget}, and \agcode{optional
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	688 qualifiers} can also be written:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	689
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	690 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	691 name -> letter \| name, letter \| name, digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	692 optional widget
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	693 -> \| widget
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	694
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	695 optional qualifiers
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	696 -> \| optional qualifiers, qualifier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	697 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	698
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	699 Note that a null production cannot \emph{follow} a vertical bar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	700
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	701 A token that has a null production is called a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	702 \index{Zero length token}\index{Token}\agterm{zero length token},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	703 since it can be represented by an empty sequence of input characters,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	704 that is to say, by nothing at all. Furthermore, even if a token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	705 doesn't have any null productions, if it has at least one rule
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	706 consisting entirely of zero length tokens it is also a zero length
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	707 token. In the Token Table window, AnaGram notes which tokens are zero
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	708 length, because they can be a source of conflicts.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	709
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	710 \subsection{Grammar Token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	711
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	712 Every grammar must have a single token which produces the entire
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	713 grammar. This token is variously called the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	714 \index{Token}\index{Grammar token}\agterm{grammar token}, the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	715 \index{Goal token}\agterm{goal token} or the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	716 \index{Start token}\agterm{start token}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	717 AnaGram provides several methods you may use to specify which token in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	718 your grammar is the grammar token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	719
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	720 You may simply use the name \agcode{grammar} for the grammar token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	721 If you wish to use some other more descriptive name for your grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	722 token, you may mark it with a following dollar sign when it appears on
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	723 the left side of a production. Alternatively, you may set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	724 \index{Grammar token}\index{Configuration parameters}\agparam{grammar token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	725 configuration parameter to specify the grammar token. Here are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	726 examples of the methods:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	727
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	728 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	729 grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	730 -> [statement \| newline]/...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	731
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	732 program \$
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	733 -> [statement \| newline]/...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	734
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	735 {}[ grammar token = program ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	736 program
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	737 -> [statement \| newline]/...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	738 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	739
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	740 If you should use more than one of these techniques, AnaGram resolves
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	741 the issue in the following manner: A marked token or a configuration
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	742 parameter setting always takes precedence over simply naming a token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	743 \agcode{grammar}. If you mark more than one token or set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	744 configuration parameter more than once, the last setting or mark wins.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	745
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	746 \subsection{Grammar Rules}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	747 \index{Rule}\index{Grammar rule}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	748
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	749 The part of a production to the right of the arrow is more often
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	750 called a \agterm{grammar rule}, or simply \agterm{rule}. A grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	751 rule is a sequence of \index{Rule elements}\agterm{rule elements},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	752 joined by commas, as in the examples of productions given above. Rule
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	753 elements are token names, character set expressions, virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	754 productions, or immediate actions (see below). Each rule element may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	755 be optionally followed by a parameter assignment. The entire rule may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	756 be followed by an optional reduction procedure. A \index{Parameter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	757 assignment}parameter assignment is a colon followed by a C variable
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	758 name. Here are some examples of rule elements with parameter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	759 assignments:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	760
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	761 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	762 '0-9':d
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	763 integer:n
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	764 expression:x
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	765 declaration:declaration{\us}descriptor
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	766 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	767
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	768 The parameters you assign to tokens in your grammar rule become the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	769 formal parameters for your \index{Reduction procedure}reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	770 procedure. The data type\index{Data type}\index{Reduction procedure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	771 arguments} of the parameter is determined by the data type for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	772 semantic value of the token to which it is assigned. If your grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	773 rule has parameter assignments, but does not have a reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	774 procedure, AnaGram will give you a warning in case the lack of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	775 reduction procedure is an oversight. If you don't need a reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	776 procedure you may safely ignore the warning. On the other hand,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	777 AnaGram has no way to determine whether you have failed to make
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	778 necessary parameter assignments. You won't find out until you compile
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	779 your parser, when your compiler will give you error messages for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	780 undefined symbols.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	781
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	782 AnaGram assigns a unique rule number to each rule in your grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	783 Rules are numbered sequentially as they are encountered in the syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	784 file. AnaGram constructs rule zero itself. Rule zero normally has a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	785 single element, the grammar token, unless you have a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	786 \agparam{disregard} statement in your grammar. In this case there
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	787 will be two elements.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	788
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	789 \subsection{Reduction Procedures}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	790 \index{Reduction procedure}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	791
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	792 % XXX somewhere in here it ought to say something like
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	793 % ``in the parsing literature reduction procedures are often known as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	794 % \agterm{semantic actions}.''
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	795 % Note that R. says there's some subtle difference between the usual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	796 % concept of semantic action and AG's concept of reduction procedure.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	797 % I don't know what this difference is and I hope she can recall it.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	798 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	799 % D. thinks this note ought to be at the end; R. wants it at the top.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	800
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	801 A \agterm{reduction procedure} is a piece of C code which optionally
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	802 follows a production. The code is executed when your parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	803 identifies the production in its input. There are two forms for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	804 reduction procedures, a short form and a long form. The short form
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	805 consists of a single C expression. The long form consists of an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	806 arbitrary block of C code. When AnaGram builds a parser, it inspects
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	807 the grammar rule to which the procedure is attached and identifies the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	808 parameters for the procedure. It uses these parameters as the formal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	809 parameters for the procedure.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	810 If the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	811 \index{Macros}\index{Allow macros}\index{Configuration switches}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	812 \agparam{allow macros}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	813 configuration switch has not been turned off, AnaGram codes the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	814 reduction procedure as a macro definition whenever possible.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	815 Otherwise AnaGram codes it as a function definition. AnaGram builds
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	816 the name for a reduction procedure by appending its internal procedure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	817 number to the string \agcode{ag{\us}rp{\us}}. Thus reduction procedures are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	818 numbered in the order in which they are encountered in the syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	819 file.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	820
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	821 Both long and short form reduction procedures are preceded by an equal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	822 sign which follows the production. The short form consists of a C or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	823 C++ expression terminated by a semicolon. When the grammar rule is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	824 reduced, the expression will be evaluated and its value will become
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	825 the value of the reduction token. The expression and the terminating
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	826 semicolon must be entirely on a single line. Note that, if you really
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	827 need to make the expression longer than will fit on one line, you can
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	828 embed a newline in a comment. Some examples of short form reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	829 procedures are:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	830
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	831 % XXX is there anything we can do about the ugly underscores?
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	832 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	833 =0;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	834
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	835 =1;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	836
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	837 =10*n + d-'0';
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	838
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	839 =
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	840 special{\us}processor(first{\us}parameter, second{\us}parameter);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	841
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	842 =word{\us}count++;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	843
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	844 =widget(constant{\us}1parameter{\us}1 + constant{\us}2parameter{\us}2 /*
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	845 {} / + constant{\us}3parameter{\us}3);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	846 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	847
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	848 A long form reduction procedure consists of an arbitrary block of C or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	849 C++ code, enclosed in braces (\bra \ket). AnaGram will code the reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	850 procedure as a function. To return a value for the reduction token,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	851 simply use the \agcode{return} statement. There are effectively no
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	852 restrictions on the content or length of a reduction procedure. Of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	853 course, if there are unbalanced braces, unterminated comments or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	854 unterminated string literals, AnaGram will not be able to determine
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	855 where the reduction procedure ends. AnaGram treats
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	856 \index{Comments}nested comments within a reduction procedure according
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	857 to the value of the \index{Nest comments}\index{Configuration
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	858 switches}\agparam{nest comments} configuration switch at the point
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	859 where it encounters the reduction procedure.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	860
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	861 From a practical point of view it is not usually good practice to have
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	862 a reduction procedure that is more than a few lines long since a long
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	863 procedure will hamper your overall view of your grammar. Long
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	864 reduction procedures should be written as separate named functions,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	865 and should either be included in the embedded C portion of your syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	866 file or should be included in a wholly separate module. Here is an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	867 example of a long form reduction procedure:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	868
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	869 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	870 =\bra
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	871 if (flag) \bra
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	872 total += x;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	873 return identify(x);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	874 \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	875 else \bra
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	876 total = 0;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	877 flag = 1;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	878 return init{\us}table(x);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	879 \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	880 \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	881 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	882
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	883 If a rule does not have a reduction procedure, the semantic value of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	884 the reduction token will be set to the \index{Semantic
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	885 value}\index{Token}\index{Value}semantic value of the first token in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	886 the rule, unless the rule is a \index{Null productions}null
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	887 production. In the latter case, the value of the reduction token will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	888 be set to zero.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	889 % XXX and what if zero isn't a valid value for the type? a compiler
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	890 % error will occur.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	891
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	892 % XXX add something like
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	893 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	894 % Variables appearing in reduction procedures which do not have a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	895 % parameter assignment in the corresponding grammar rule can be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	896 % declared globally or (file)-statically in your embedded C, or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	897 % alternatively could be added to the parser control block using
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	898 % the \agparam{extend pcb} statement (q.v. \| See Section ....).
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	899 % (Reword this.)
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	900 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	901 % Should also discuss the sequencing of reduction procedure calls
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	902 % so that people understand what happens if you use such variables.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	903 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	904 % also ``A reduction procedure can be used to terminate parsing for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	905 % semantic reasons''.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	906 %
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	907
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	908 \subsection{Immediate Actions}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	909 \index{Immediate action}\index{Action}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	910
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	911 An immediate action is a rule element that consists of executable C or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	912 C++ code embedded within a grammar rule to be executed when it is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	913 encountered. An immediate action is denoted by the use of an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	914 exclamation point, \index{!}``!''. The content of an immediate action
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	915 may be written following the rules for either long form or short form
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	916 reduction procedures. As with any other rule element, it must be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	917 separated from preceding and following rule elements by commas. In
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	918 the grammar for a simple desk calculator, one might write
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	919
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	920 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	921 transaction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	922 -> !printf('\#');, expression:x = printf("\%d{\bs}n", x);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	923 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	924
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	925 % XXX s/apparent/visible/
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	926 Notice that the only apparent difference between an immediate action
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	927 and a reduction procedure is that the immediate action is preceded by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	928 ``!'' instead of ``=''. The immediate action must be followed by a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	929 comma to separate it from the following rule element.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	930
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	931 Immediate actions may also be used in definitions:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	932
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	933 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	934 prompt = !printf('\#');
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	935 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	936
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	937 AnaGram implements an immediate action by creating a special token for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	938 it. AnaGram then creates a single null production for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	939 token. Finally, the immediate action is implemented as the reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	940 procedure for the null production.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	941
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	942 For example, you could implement \agcode{prompt} by writing a null production
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	943 with a reduction procedure:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	944
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	945 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	946 prompt
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	947 -> = printf('\#');
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	948 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	949
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	950 This production would be equivalent to the definition above.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	951
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	952 There are two ways, however, in which immediate actions differ from
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	953 the equivalent null production. Immediate actions may access any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	954 parameter assignments which precede them in the rule in which they
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	955 occur. On the other hand, there is no way to assign a data type to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	956 the semantic value, if any, returned by the immediate action.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	957 Therefore, the type is determined by your setting of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	958 \index{Default token type}\index{Configuration parameters}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	959 \agparam{default token type} configuration parameter.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	960
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	961 \subsection{Virtual Productions}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	962 \index{Virtual productions}\index{Production}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	963
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	964 Virtual productions are a convenient short form notation for common
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	965 grammatical constructs involving choice and repetition. The notation
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	966 represents an extension of notation commonly used in programming
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	967 manuals. A virtual production may be written in a grammar rule at any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	968 place where you could write a token name, even within another virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	969 production. Note that use of virtual productions is never
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	970 \emph{required}, since the equivalent productions can always be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	971 written out explicitly instead.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	972
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	973 When AnaGram encounters a virtual production, it replaces the virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	974 production with a new token and writes appropriate productions for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	975 new token. When you look at your syntax tables using AnaGram windows,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	976 you will see the productions that AnaGram generates. AnaGram keeps a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	977 record of virtual productions, so that generally if you use the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	978 virtual production a second time, you get the same set of tokens and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	979 productions that were generated the first time it was used. This is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	980 not the case if the virtual productions contain reduction procedures
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	981 or immediate actions, since AnaGram is not equipped to determine
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	982 whether two pieces of C code are equivalent. Thus, a virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	983 production that contains a reduction procedure will be unique and will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	984 not be reused.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	985
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	986 One disadvantage of virtual productions is that there is no way to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	987 specify the data type of the \index{Semantic value}\index{Virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	988 production}semantic value of a virtual production. Therefore, if you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	989 have a reduction procedure within a virtual production, its return
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	990 value must be consistent with the type defined by the \index{Default
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	991 token type}\index{Configuration parameters}\agparam{default token type}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	992 configuration parameter.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	993
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	994 The simplest virtual production is the \index{Token}\index{Optional
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	995 token}\agterm{optional token}. If \agcode{x} is an arbitrary token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	996 name or set expression, you can indicate an optional \agcode{x} by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	997 writing \index{?}\agcode{x?}. You may also indicate a repetition of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	998 \agcode{x} by using the ellipsis with either \agcode{x} or \agcode{x?}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	999 \index{...}\index{Ellipsis}Thus \agcode{x...} represents
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1000 one or more instances of \agcode{x} and \index{?...}\agcode{x?...}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1001 represents zero or more instances of \agcode{x}. For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1002
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1003 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1004 '+'?
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1005 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1006
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1007 can be used to represent an optional plus sign, that is, a choice
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1008 between a plus sign and nothing at all. Similarly,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1009
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1010 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1011 '{\bs}n'?...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1012 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1013
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1014 represents an optional sequence of newline characters.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1015
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1016 \index{Brackets}\index{Braces}\index{\_opb\_clb}\index{[]}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1017 The next category of virtual productions uses brackets or braces to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1018 indicate a choice among a number of enclosed grammar rules separated
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1019 by vertical bars. A single rule may also be enclosed. Note that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1020 \emph{rules}, with following reduction procedures, are allowed, not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1021 simply tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1022
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1023 Braces are used to indicate that one option must be chosen. Brackets
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1024 are used to indicate the choice is optional, i.e. may be omitted
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1025 altogether. The ellipsis following a set of options within brackets
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1026 or braces indicates the option may be repeated an indefinite number of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1027 times.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1028
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1029 You can use braces to indicate a simple choice among a number of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1030 options. A Cobol grammar offers the following choice of equivalent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1031 keywords:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1032
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1033 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1034 \bra "RECORD", "IS"? \| "RECORDS", "ARE"? \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1035 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1036
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1037 \index{\_opb\_clb...}\index{ []...}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1038 You may use the ellipsis with braces to indicate an arbitrary positive
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1039 number of repetitions of the choice:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1040
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1041 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1042 {\bra}type specifier \| storage class specifier{\ket}...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1043 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1044
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1045 This expression requires at least one type specifier or storage class
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1046 specifier, but will accept any number.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1047
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1048 \index{[]}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1049 To make a choice optional, use brackets instead of braces. An
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1050 example, again drawn from a Cobol grammar, is:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1051
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1052 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1053 {}["LIMIT", "IS"? \| "LIMITS", "ARE"?]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1054 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1055
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1056 \index{[]...}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1057 Ellipses may be used with brackets to indicate an arbitrary number of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1058 choices that may be omitted altogether:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1059
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1060 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1061 {}[argument, [',', argument]...]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1062 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1063
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1064 This expression describes an optional argument list with arguments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1065 separated by commas.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1066
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1067 If you use a null production within braces, it must be the first option:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1068
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1069 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1070 \bra \| '+' \| '-' \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1071 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1072
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1073 Normally, you would do this only if you wanted to attach a reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1074 procedure to the null production. Note that if you include a null
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1075 production within braces, and add an ellipsis after the closing brace
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1076 for repetition, your grammar will be ambiguous. Just exactly how many
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1077 times does the null production occur? Use brackets instead, and omit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1078 the null production.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1079
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1080 Null productions are not allowed with brackets, since they would be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1081 intrinsically ambiguous.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1082
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1083 The options within braces or brackets may be grammar rules of any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1084 length or complexity and may themselves contain virtual productions of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1085 arbitrary complexity. Nevertheless, in practice, clarity suffers as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1086 soon as the options get very complex. Virtual productions are most
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1087 important and useful when used in simple situations. In those
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1088 situations they will enhance the clarity of your grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1089
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1090 Here is an example that is moderately complex, even though each rule
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1091 consists of a single token:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1092
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1093 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1094 \bra{\bra}"on" \| "true"\ket = 1; \| {\bra}"off" \| "false"\ket = 0; \| integer\ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1095 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1096
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1097 This example can be used to allow as input either an integer or, for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1098 special cases, keywords. You could write this option out in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1099 following way:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1100
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1101 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1102 p1
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1103 -> p2 = 1;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1104 -> p3 = 0;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1105 -> integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1106
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1107 p2
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1108 -> "on"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1109 -> "true"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1110
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1111 p3
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1112 -> "off"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1113 -> "false"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1114 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1115
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1116 The final category of virtual production provides a notation for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1117 \index{Alternating sequence}\agterm{alternating sequences}. An
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1118 alternating sequence is a set of choices which may be repeated
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1119 arbitrarily subject to the side condition that no choice may follow
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1120 itself, in other words, that the choices must alternate. Alternating
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1121 sequences are written with either brackets or braces depending on
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1122 whether the sequence is optional or not, followed by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1123 \index{/...}``\agcode{/...}''. Note that the choices themselves may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1124 allow sequences. For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1125
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1126 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1127 program
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1128 -> [statement \| newline...]/..., eof
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1129 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1130
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1131 represents a sequence of statements separated by one or more newlines.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1132 Any two statements must be separated by one or more newline
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1133 characters, and newlines may also appear at the beginning and the end
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1134 of the program.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1135
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1136 Null productions are not allowed within alternating sequences, since
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1137 they are intrinsically ambiguous in all cases.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1138
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1139 \subsection{Definition Statements}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1140 \index{Definitions}\index{Definition statement}\index{Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1141
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1142 A definition statement is simply a shorthand way of naming a character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1143 set, a \index{Virtual productions}\index{Production}virtual
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1144 production, a keyword string, or an immediate action. It can also be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1145 used for providing an alternate name for a token. Definitions have the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1146 form:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1147
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1148 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1149 name = \codemeta{character set}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1150 name = \codemeta{virtual production}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1151 name = \codemeta{keyword}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1152 name = \codemeta{immediate action}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1153 name = \codemeta{token name}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1154 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1155
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1156 The name may be any name acceptable to AnaGram. The name can then be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1157 used anywhere you might have used the expression on the right
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1158 side. \index{!}For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1159
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1160 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1161 upper case letter = 'A-Z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1162 lower case letter = 'a-z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1163 letter = upper case letter + lower case letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1164 statement list = statement?...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1165 while keyword = "WHILE"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1166 prompt = !printf("Please enter name:");
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1167 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1168
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1169 It is important to recognize that a definition statement that names a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1170 set does not define a token. A token is defined only when the set is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1171 used in a grammar rule, and then only if the set is used directly, not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1172 in combination with some other set. Furthermore, if you use a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1173 character set directly in a grammar rule, and in some other rule you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1174 use a name that refers to the same set of characters, you will get two
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1175 different tokens. For example, if you have defined \agcode{upper case
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1176 letter} as in the above example and use both \agcode{upper case
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1177 letter} and \agcode{'A-Z'} in grammar rules, AnaGram will assign
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1178 different \index{Token number}\index{Token}\index{Number}token numbers
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1179 to accommodate any differences in attributes you may assign to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1180 tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1181
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1182 Renaming tokens is a convenient way to connect two independently
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1183 written portions of a grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1184 % See the C grammar in the EXAMPLES directory of your distribution
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1185 % disk for an example.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1186
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1187 \subsection{Embedded C}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1188 \index{Embedded C}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1189
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1190 You may encapsulate C or C++ code in your syntax file by enclosing it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1191 in braces (\bra \ket). Such pieces of code are copied to the parser file
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1192 untouched, in the order they are found in the syntax file. There may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1193 be any number of such pieces of embedded C. The only restriction is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1194 that they must not start on the same line as some other AnaGram
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1195 statement, and following AnaGram statements must also start on fresh
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1196 lines.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1197
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1198 Normally, the blocks of embedded C in your syntax file are copied to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1199 the parser file \emph{following} a set of definitions and declarations
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1200 AnaGram needs for the code it generates. However, if the \emph{first}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1201 statement in your \index{Syntax file}syntax file is a block of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1202 embedded C, it will \emph{precede} AnaGram's definitions and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1203 declarations. This block of embedded C is called the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1204 \index{Prologue}\index{C prologue}``C prologue''. There are two main
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1205 reasons for this special treatment. First, you may want to have a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1206 title and \index{Copyright notice}copyright notice in your parser. If
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1207 you include them in an initial block of embedded C they will be right
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1208 at the beginning of both your syntax file and your parser file.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1209 Second, if some of your tokens have data type\index{Token}\index{Data
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1210 type}s other than those predefined in C or C++, you may include the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1211 definitions here, so they will be available to the code AnaGram
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1212 generates.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1213
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1214 AnaGram scans embedded C only insofar as is necessary to find the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1215 closing right brace. Therefore any braces used within embedded C must
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1216 balance properly. AnaGram skips braces enclosed in character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1217 constants and string literals, as well as braces enclosed in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1218 comments. It also recognizes C++ style comments that begin with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1219 \agcode{//}. \index{Comments}Treatment of nested versus non-nested comments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1220 is controlled by the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1221 \index{Nest comments}\index{Configuration switches}\agparam{nest comments}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1222 configuration parameter. AnaGram will use the status of this
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1223 parameter in effect at the beginning of the section of embedded C.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1224
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1225 AnaGram, of course, can be confused by unterminated strings,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1226 unbalanced brackets, and unterminated comments. The most likely
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1227 outcome, in such a situation, is that AnaGram will encounter the end
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1228 of file looking for the end of the embedded C. Should this happen,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1229 AnaGram will identify the beginning of the piece of embedded C which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1230 caused the problem.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1231
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1232 The code you include as embedded C, of course, has to coexist with the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1233 code AnaGram generates. In order to keep the potential for conflicts
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1234 to a minimum, all variables and functions which AnaGram defines begin
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1235 either with the name of your parser or with the letters
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1236 \agcode{ag{\us}}. You should avoid variable names which begin with these
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1237 letters.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1238
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1239 Reduction procedures are copied to the \index{Parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1240 file}\index{File}parser file in the order in which they are defined
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1241 \emph{following} all of the embedded C. Thus your reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1242 procedures may freely use variables and macros defined anywhere in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1243 your embedded C.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1244
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1245 \subsection{Configuration Sections}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1246 \index{Configuration section}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1247
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1248 A configuration section is a special section of your syntax file
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1249 enclosed in brackets. Within a configuration section you may set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1250 values of configuration parameters or switches, or you may use one or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1251 more of several available attribute statements to specify special
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1252 treatment for certain tokens. There can be as many or as few
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1253 configuration sections in your syntax file as you wish. Each
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1254 configuration section must begin on a new line. Any AnaGram statement
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1255 which follows a configuration section must also begin on a new line.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1256
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1257 Within a configuration section, each parameter setting and each
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1258 attribute statement must begin on a new line. The rules for using
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1259 comments and continuation lines are the same as for the rest of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1260 AnaGram.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1261
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1262 Configuration parameters control the way AnaGram interprets your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1263 syntax file and the way it builds your parser. A full discussion of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1264 the use of configuration parameters, including a complete discussion
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1265 of each parameter and its default value, is given in Appendix A.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1266
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1267 \index{Attribute statements}\index{Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1268 Attribute statements comprise the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1269 \index{Precedence declarations}precedence declarations \agparam{left},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1270 \agparam{right}, and \agparam{nonassoc}; the \agparam{sticky}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1271 declaration; the \agparam{distinguish keywords} statement; the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1272 \agparam{hidden} declaration; the \agparam{disregard} and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1273 \agparam{lexeme} statements; the \agparam{enum} statement; the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1274 \index{Reserve keywords}\agparam{reserve keywords} declaration; and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1275 the \index{Rename macro}\agparam{rename macro} statement.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1276
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1277 The precedence declarations and the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1278 \index{Sticky declaration}\index{Declaration}\agparam{sticky}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1279 declaration may be used to resolve conflicts in your grammar. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1280 \agparam{distinguish keywords} statement may be used to control
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1281 keyword recognition. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1282 \index{Hidden declaration}\index{Declaration}\agparam{hidden}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1283 declaration causes certain token names not to be used when your parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1284 produces
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1285 \index{Syntax error}\index{Errors}\index{Error messages}syntax error
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1286 messages. You may use the \agparam{disregard} and \agparam{lexeme}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1287 statements to cause your parser to skip automatically over certain
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1288 tokens in its input. The \agparam{enum} statement is almost identical
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1289 to the enum statement in C. It can be used to assign names to input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1290 codes in grammars which are taking input from a \index{Lexical
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1291 scanner}lexical scanner or another parser. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1292 \index{Reserve keywords}\agparam{reserve keywords} declaration allows
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1293 you to specify certain keywords as reserved words. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1294 \index{Rename macro}\agparam{rename macro} statement allows you to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1295 override the names AnaGram uses for various macro definitions it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1296 creates in the code it generates.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1297
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1298 Attribute statements are discussed below. Except for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1299 \agparam{disregard} and \agparam{rename macro} statements, attribute
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1300 statements accept lists of operands enclosed in braces (\bra \ket)
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1301 and separated by commas. A dangling comma following the last item in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1302 a list will be ignored.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1303
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1304 \subsection{Setting Configuration Parameters}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1305 \index{Configuration parameters}\index{Parameters}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1306
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1307 Each configuration parameter has a name that follows the AnaGram
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1308 conventions for symbol names, except that AnaGram ignores
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1309 case\index{Case sensitivity} when looking up configuration parameter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1310 names.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1311
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1312 There are a number of varieties of configuration parameters. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1313 simplest,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1314 \index{Configuration switches}\index{Switches}configuration switches,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1315 simply turn some feature of AnaGram on or off. These parameters need
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1316 simply be stated to turn the feature on, or negated with the tilde
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1317 (\agcode{\~{}}) to turn the feature off:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1318
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1319 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1320 nest comments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1321 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1322
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1323 causes AnaGram to allow nested comments, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1324
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1325 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1326 \~{}nest comments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1327 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1328
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1329 causes AnaGram to disallow nested comments.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1330
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1331 You may also set or reset configuration switches with explicit on or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1332 off values:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1333
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1334 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1335 nest comments = on
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1336 nest comments = off
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1337 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1338
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1339 The remaining configuration parameters are assigned values using a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1340 simple assignment statement. Depending on the parameter, the value it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1341 takes may be the name of a token, a C variable name, a C or C++ data
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1342 type, a string constant or an integer. String constants are written
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1343 using the same rules as keyword strings, described above.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1344
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1345 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1346 grammar token = program
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1347 parser name = widget
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1348 default token type = void *
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1349 header file name = "widget.h"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1350 parser stack size = 50
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1351 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1352
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1353 A number of string-valued \index{Configuration
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1354 parameters}configuration parameters are used to determine file
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1355 names and variable names. In these parameters, the \index{\#}``\#'',
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1356 \index{\_dol}``\$'', and ``\index{ \_prc}\%'' characters
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1357 are used as wild cards. In file name specifications and the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1358 specification of the name of your parser, ``\#'' will be replaced by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1359 the name of your syntax file. In other function and variable names
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1360 AnaGram creates while building your parser, ``\$'' will be replaced by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1361 the name of your parser. When building enumeration constants for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1362 names of the tokens in your grammar, ``\%'' will be replaced by the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1363 name of the token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1364
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1365 Note that when entering a Windows/DOS path name as a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1366 value for a file name parameter you must quote any backslashes in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1367 path name. For example,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1368
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1369 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1370 coverage file name = "f:{\bs\bs}sna{\bs\bs}foo.nrc"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1371 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1372
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1373 \subsection{Precedence Declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1374 \index{Precedence declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1375
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1376 AnaGram allows you to resolve shift-reduce conflicts by assigning
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1377 precedence levels to operators. There are three precedence
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1378 declarations available, beginning with the keywords
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1379 \index{Left}\agparam{left}, \index{Right}\agparam{right}, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1380 \index{Nonassoc}\agparam{nonassoc} respectively. Each such
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1381 declaration consists of the appropriate keyword and a list of tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1382 enclosed in braces (\bra \ket). All the tokens in the list have the same
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1383 precedence, higher than tokens in any previous declaration and lower
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1384 than in any subsequent declaration. If the keyword is \agparam{left},
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1385 the tokens will group to the left. If it is \agparam{right}, they
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1386 will group to the right. If it is \agparam{nonassoc} (for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1387 non-associative) no grouping will be assumed. Precedence declarations
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1388 must be included in a configuration section. Here are precedence
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1389 declarations appropriate to a simple desk calculator program:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1390
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1391 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1392 {}[
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1393 left \bra '+', '-' \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1394 left \bra star, '/', '\%' \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1395 right \bra unary minus \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1396 ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1397 unary minus = '-'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1398 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1399
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1400 Note that \agcode{unary minus} and \agcode{'-'} can have different
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1401 precedence.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1402
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1403 Precedence declarations are one of the few instances in AnaGram where
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1404 the \index{Statements}\index{Order of statements}order of statements
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1405 is significant.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1406
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1407 The use of precedence declarations is discussed in Chapter 9.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1408
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1409 \subsection{``Sticky'' Declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1410 \index{Sticky declaration}\index{Declaration}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1411
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1412 AnaGram provides another means for resolving shift-reduce conflicts.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1413 You may characterize any token as ``sticky''. Then, in the case of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1414 \index{Shift-reduce conflict}\index{Conflicts}shift-reduce conflict
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1415 where a ``sticky'' token is the last token in the input buffer, the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1416 conflict will be resolved by selecting the shift operation.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1417 Intuitively, you may think of this as though the ``sticky'' token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1418 adheres to and draws in any subsequent input that it can. ``Sticky''
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1419 declarations are included in configuration sections. They begin with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1420 the keyword \agcode{sticky} followed by a list of tokens, separated by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1421 commas inside braces (\bra \ket). Suppose, for instance, you wished to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1422 pick up a line of text, skipping any leading space or tab
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1423 characters. You might write the following syntax:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1424
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1425 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1426 white space = ' ' + '{\bs}t'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1427
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1428 text char
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1429 -> \~{}'{\bs}n':c = do{\us}something(c);
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1430
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1431 line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1432 -> leading white space, text char?..., '{\bs}n'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1433
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1434 leading white space
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1435 ->
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1436 -> leading white space, white space
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1437 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1438
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1439 Unfortunately, this syntax is ambiguous, since space and tab are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1440 legitimate instances of both leading white space and text char. What
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1441 you really want to do is to skip white space until you find a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1442 non-blank character and then you want to accept all characters to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1443 end of the line. There are two ways to address the problem. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1444 first is to define a special token for the first non-blank character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1445 and, using it, to write an unambiguous grammar. This approach, while
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1446 laudable, is tedious and prolix. Instead, use \agparam{sticky} to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1447 resolve the problem:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1448
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1449 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1450 {}[ sticky \bra leading white space \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1451 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1452
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1453 Now when AnaGram analyzes your grammar, and encounters the ambiguity,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1454 it will understand that a blank or tab that could be treated either as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1455 leading white space or the as the first text character should be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1456 treated as white space. Since \agcode{leading white space} is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1457 ``sticky'', any subsequent white space adheres to it.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1458
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1459 As with conflicts resolved with precedence levels, AnaGram lists all
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1460 conflicts that it resolves using \agcode{sticky} in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1461 \index{Resolved Conflicts}\index{Window}\agwindow{Resolved Conflicts
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1462 Table}, so you can verify that the conflicts have been correctly
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1463 resolved.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1464
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1465 An important use of sticky tokens is to inhibit the recognition of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1466 following \index{Keywords}keywords. Following a sticky token, a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1467 keyword, which, according to your grammar, would otherwise be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1468 legitimate input, will not be recognized if a shift action is possible
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1469 for the first character of the keyword. For example, imagine that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1470 \agcode{name} has been defined in the conventional way, and there
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1471 exists a production with name followed immediately by the keyword
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1472 \agcode{int}. Then if, in your input, the word \agcode{print} were to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1473 occur, your grammar would parse it as a name, \agcode{pr}, followed by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1474 the keyword \agcode{int}. If you make \agcode{name} sticky, however,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1475 the first letter of \agcode{int} will be seen to be an acceptable
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1476 character for \agcode{name} and the keyword will not be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1477 recognized. Your parser will then recognize the \agcode{name} as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1478 \agcode{print}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1479
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1480 \subsection{Distinguish Keywords Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1481 \index{Distinguish keywords}\index{Keywords}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1482
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1483 Distinguish keywords statements are occasionally needed to prevent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1484 keyword recognition. You may, for example, wish to prevent the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1485 recognition of the keyword \agcode{int} when it occurs embedded in a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1486 word such as \agcode{interval}. Of course, you need to do this only
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1487 if both the keyword and the other word are both legitimate input at
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1488 the same point in your grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1489
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1490 A distinguish keywords statement can prevent recognition of a keyword
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1491 which is embedded in another word provided at least one character of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1492 the other word follows the keyword.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1493
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1494 The distinguish keywords statement has the form:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1495
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1496 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1497 distinguish keywords \bra \codemeta{list of character sets} \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1498 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1499
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1500 AnaGram compares all the characters in each keyword to the characters
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1501 included in each character set in turn. If it finds that all the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1502 characters in a keyword are members of a particular set, it tells the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1503 keyword recognition logic to try to match the keyword only against the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1504 longest sequence of characters drawn from the specified set. In other
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1505 words, in order for a keyword to be recognized, the keyword
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1506 \emph{must} be followed by a character \emph{not} in the set. The set
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1507 associated with a keyword is the first one in the list which contains
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1508 all the characters found in the keyword. If you have more than one
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1509 \agparam{distinguish keywords} statement in your grammar, the lists
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1510 are tried in the order in which they appear in the grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1511
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1512 The purpose of the \agparam{distinguish keywords} statement is to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1513 enable your parser to distinguish a keyword from the same sequence of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1514 characters embedded within another sequence. Thus suppose that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1515 \agcode{int} is a keyword, and, according to your grammar, could
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1516 appear in the same place as the word \agcode{integral}. If you don't
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1517 want it to be recognized as a keyword in these circumstances, you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1518 would write the following distinguish statement:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1519
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1520 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1521 distinguish keywords \bra 'a-z'+'A-Z' \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1522 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1523
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1524 To also inhibit recognition of \agcode{int} within \agcode{print}, you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1525 would combine the use of the distinguish keywords statement with the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1526 \agparam{sticky} declaration.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1527
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1528 \subsection{``Hidden'' Declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1529 \index{Hidden declaration}\index{Declaration}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1530
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1531 AnaGram provides an optional \index{Error diagnosis}error diagnosis
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1532 feature for your parser (see Chapter 9). The \agparam{hidden}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1533 declaration allows you to identify tokens that you do not wish to be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1534 used in making up \index{Diagnostic messages}diagnostic messages.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1535 These tokens are tokens whose names would not mean anything to your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1536 users. The format of a ``hidden'' declaration is the same as that of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1537 precedence and ``sticky'' declarations. Within a configuration
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1538 section, the keyword ``hidden'' is followed by a list of tokens. For
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1539 example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1540
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1541 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1542 {}[ hidden \bra comment head \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1543 comment
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1544 -> comment head, "*/"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1545
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1546 comment head
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1547 -> "/*"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1548 -> comment head, \~{}eof
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1549 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1550
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1551 This is an AnaGram representation of ANSI standard C comments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1552 (non-nested). In this example the token \agcode{comment head} exists
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1553 only for convenience in writing the grammar and has no particular
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1554 meaning to an end user. On the other hand, he knows what the word
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1555 \agcode{comment} refers to. The ``hidden'' attribute will cause AnaGram's
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1556 diagnostic builder, by backing up the stack until it finds a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1557 non-hidden token, to eschew \agcode{comment head} in favor of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1558 \agcode{comment}.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1559 % XXX eschew obfuscation. how about ``avoid''?
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1560
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1561 \subsection{Disregard Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1562
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1563 The purpose of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1564 \index{Disregard statement}\index{Statement}\agparam{disregard}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1565 statement is to skip over uninteresting \index{White space}white space
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1566 and comments in your input files. The disregard statement allows you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1567 to specify a token that should be passed over in the input to your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1568 parser. The statement takes the form:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1569
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1570 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1571 disregard ws
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1572 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1573
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1574 where \agcode{ws} is a token name or character set. Disregard
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1575 statements may be placed in any configuration section.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1576
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1577 You may have more than one disregard statement in your grammar. If
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1578 you do, AnaGram will create a shell production. For example, suppose
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1579 you write:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1580
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1581 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1582 {}[
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1583 disregard alpha
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1584 disregard beta
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1585 ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1586 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1587
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1588 AnaGram will proceed as though you had written:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1589
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1590 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1591 gamma
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1592 -> alpha \| beta
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1593 {}[ disregard gamma ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1594 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1595
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1596 It frequently happens that you wish your parser to disregard blanks or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1597 comments, except that white space within names, numbers, strings, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1598 other elementary constructs is subject to special rules and thus
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1599 should not be disregarded blindly. In this case, you can use the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1600 \agparam{lexeme} statement to declare these constructs off limits
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1601 for the disregard statement. Within these constructs, the disregard
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1602 statement will be inoperative and the admissibility of white space
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1603 will be determined solely by the productions which define these
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1604 constructs.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1605
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1606 Outside those productions which define lexemes, you should not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1607 generally use a token which is supposed to be disregarded. If you do,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1608 your grammar will have conflicts, since the token could satisfy both
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1609 the explicit usage and the implicit rules set up by the disregard
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1610 statement. Such conflicts, however, are resolved automatically in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1611 favor of your explicit use of the token. The conflicts will appear in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1612 the \agwindow{Resolved Conflicts} window.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1613 % XXX I'm not sure that's still true.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1614
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1615 In order to implement the disregard statement AnaGram will redefine
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1616 some tokens in your grammar. For example, \agcode{+} may be redefined
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1617 to consist of a simple plus sign followed by optional white space:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1618
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1619 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1620 '+'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1621 -> '+'\%, white space?...
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1622 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1623
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1624 The percent sign is used to indicate the original, simple plus sign
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1625 without the optional white space attached. You will probably notice
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1626 the percent sign appearing in some windows and traces. In earlier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1627 versions of AnaGram, the degree sign, ``\agcode{\degrees}'', was used rather
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1628 than ``\agcode{\%}''.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1629
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1630 \subsection{Lexeme Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1631
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1632 The ``lexeme'' \index{Statement}\index{Lexeme statement}statement is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1633 used to fine-tune the disregard statement.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1634 The lexeme statement takes the form:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1635
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1636 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1637 {}[ lexeme \bra \codemeta{nonterminal token list} \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1638 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1639
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1640 where \textit{nonterminal token list} is a list of nonterminal tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1641 separated by commas.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1642 Lexeme statements may be placed in any configuration section, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1643 there may be any number of them.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1644
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1645 When you specify that a token is to be disregarded, AnaGram rewrites
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1646 your grammar so that the token will be passed over whenever it occurs
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1647 at the beginning of a file or following a lexical unit, or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1648 \agterm{lexeme}. If you have no \agparam{lexeme} statement, then the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1649 lexemes in your grammar are just the terminal tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1650
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1651 The \agparam{lexeme} statement allows you to specify that certain
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1652 nonterminal tokens are also to be treated as lexemes. This means that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1653 the disregard token will be skipped following the lexeme, but not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1654 between the characters that constitute the lexeme.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1655
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1656 Lexemes correspond to the tokens that a lexical scanner, if you were
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1657 using one, would commonly identify and pass to a parser as single
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1658 tokens. You don't usually wish to disregard white space within these
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1659 tokens. For example, in a grammar for a conventional programming
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1660 language where blank characters are to be disregarded, you might
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1661 include:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1662
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1663 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1664 {}[ lexeme \bra string, character constant, name, number \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1665 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1666
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1667 since blank characters must not be overlooked within strings and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1668 character constants and should not be permitted within names or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1669 numbers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1670
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1671 Normally, AnaGram considers the disregard token to be optional;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1672 however there are circumstances where treating the disregard token as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1673 optional would lead to conflicts: two successive names, or two
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1674 successive numbers, for example. In this case, you would like to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1675 require that the lexemes be separated by instances of the disregard
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1676 token. To do this, simply set the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1677 \index{Distinguish lexemes}\index{Configuration switches}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1678 \agparam{distinguish lexemes}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1679 configuration switch.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1680 When this switch is set, AnaGram will ensure that disregard tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1681 will be required in those situations where making them optional would
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1682 lead to conflicts.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1683
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1684 White space may be used explicitly within definitions of lexeme tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1685 in your grammar if desired, without causing conflicts. Thus, if you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1686 wish to allow embedded space in variable names, you might write:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1687
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1688 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1689 {}[
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1690 disregard space
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1691 lexeme \bra variable name \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1692 ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1693 space = ' ' + '{\bs}t'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1694 letter = 'a-z' + 'A-Z'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1695 digit = '0-9'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1696
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1697 variable name
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1698 -> letter
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1699 -> variable name, letter + digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1700 -> variable name, space..., letter + digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1701 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1702
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1703 \subsection{Enum Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1704 \index{Enum statement}\index{Enumeration}\index{Token}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1705
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1706 The \agparam{enum} statement follows rules nearly identical to those
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1707 for C and C++. This makes it possible to copy an enum statement from
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1708 your syntax file to a program file written in either C or C++, without
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1709 any need for editing. The only differences are that AnaGram makes no
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1710 provision for blank lines within the enumeration list, nor does it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1711 accept a type name. The \agparam{enum} statement is equivalent to a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1712 corresponding set of definition statements. It is especially useful
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1713 when a parser is accepting token input from another program, a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1714 \index{Lexical scanner}lexical scanner, for example. Using
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1715 the enum statement you may conveniently define all the identification
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1716 codes for the input tokens.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1717
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1718 Each entry in an enum statement may be either a name, or a name
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1719 followed by an ``='' sign and a character representation. If there is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1720 a character representation the name is assigned the value of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1721 specified character. Otherwise it is assigned a value one more than
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1722 that assigned to the previous name. If the first name in the list is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1723 not given an explicit value, it will be given the value zero. For
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1724 example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1725
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1726 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1727 {}[
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1728 enum \bra
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1729 eof, a,b,c,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1730 blank = '\ ', x, y
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1731 \ket
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1732 ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1733 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1734
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1735 is equivalent to the following definition statements
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1736
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1737 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1738 eof = 0
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1739 a = 1
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1740 b = 2
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1741 c = 3
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1742 blank = '\ '
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1743 x = 33
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1744 y = 34
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1745 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1746
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1747 \subsection{Subgrammar Declarations}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1748 \index{Subgrammar declaration}\index{Declaration}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1749
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1750 A \agparam{subgrammar} declaration can be a useful way to deal with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1751 conflicts in certain situations. It tells AnaGram to treat the tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1752 listed in the declaration as though they were each grammar tokens,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1753 each specifying a complete subgrammar in itself, and, in determining
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1754 shift and reduction actions, to ignore the usage of the tokens in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1755 larger grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1756
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1757 In some cases it is perfectly reasonable to ignore usage. The most
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1758 common example occurs when building a lexical scanner for a language
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1759 such as C as in the example in Section 7.4.4. In this case, you can
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1760 write a complete grammar for a C token with no difficulty. But if you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1761 try to extend it to a sequence of tokens, you get scores of conflicts.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1762 This situation arises because you specify that any C token can follow
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1763 another, when in actual practice, an identifier, for example, cannot
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1764 follow another identifier without some intervening space or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1765 punctuation.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1766
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1767 It is theoretically possible, but in practice quite awkward, to write
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1768 a grammar for a sequence of tokens so that there are no conflicts.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1769 The subgrammar declaration provides a way around this problem by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1770 telling AnaGram that when it is looking for reducing tokens for any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1771 rule produced directly or indirectly by a subgrammar token, it should
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1772 disregard the usage of the token and only consider usage internal to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1773 the definition of the subgrammar token, as though the subgrammar token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1774 were the start token of the grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1775
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1776 The subgrammar declaration is made in a configuration section and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1777 consists of the keyword \agcode{subgrammar} followed by a list of one
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1778 or more nonterminal token names, separated by commas and enclosed in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1779 braces (\bra \ket). For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1780
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1781 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1782 {}[ subgrammar \bra C token, word \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1783 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1784
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1785 Since the subgrammar statement changes the way AnaGram determines
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1786 reducing tokens, it should be used with caution. You should be sure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1787 that the conflicts you are eliminating are really inconsequential.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1788
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1789 \subsection{Reserve Keywords Declaration}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1790 \index{Reserve keywords}\index{Keywords}\index{Keyword anomalies}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1791
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1792 The \agparam{reserve keywords} declaration can be used to specify a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1793 list of keywords that are reserved and cannot be used except as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1794 explicitly specified in the grammar. This enables AnaGram to avoid
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1795 issuing meaningless keyword anomaly diagnostics (see \S 7.5). AnaGram
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1796 does not automatically presume that keywords are also reserved words,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1797 since in many grammars there is no need to specify reserved words.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1798
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1799 The reserve keywords declaration is made in a configuration section
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1800 and consists of the words \agcode{reserve keywords} followed by a list
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1801 of one or more keyword strings, separated by commas and enclosed in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1802 braces (\bra \ket). For example:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1803
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1804 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1805 {}[ reserve keywords \bra "int", "char", "float", "double" \ket ]
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1806 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1807
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1808 \subsection{Rename Macro Statement}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1809 \index{Rename macro}\index{Macros}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1810
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1811 AnaGram uses a number of macros in its generated code. It is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1812 possible, therefore, to run into naming collisions with other
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1813 components of your program. The \agparam{rename macro} statement
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1814 allows you to change the name AnaGram uses for a particular macro to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1815 avoid these problems. For example, the Windows NT operating system
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1816 uses \agcode{CONTEXT} structures to perform various internal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1817 operations. If you use the context tracking option (see \S 9.5.4)
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1818 your parser will have a macro called \agcode{CONTEXT}. To avoid the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1819 name collision, add the following statement to any configuration
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1820 section in your grammar:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1821
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1822 \begin{indentingcode}{0.4in}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1823 rename macro CONTEXT AG{\us}CONTEXT
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1824 \end{indentingcode}
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1825
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1826 Then, simply use \agcode{AG{\us}CONTEXT} where you would otherwise have
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	1827 used \agcode{CONTEXT}.

Mercurial > ~dholland > hg > ag > index.cgi

annotate doc/manual/sf.tex @ 21:1c9dac05d040