AnaGram interim repo (temporary): doc/misc/html/isdp.html annotate

annotate doc/misc/html/isdp.html @ 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 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	2 <HTML>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	3 <HEAD>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	4 <TITLE>Introduction to Syntax Directed Parsing</TITLE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	5 </HEAD>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	6
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	7 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	8 TEXT="#000000" LINK="#0033CC"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	9 VLINK="#CC0033" ALINK="#CC0099">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	10
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	11 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	12
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	13 <IMG ALIGN="right" SRC="images/agrsl6c.gif" ALT="AnaGram"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	14 WIDTH=124 HEIGHT=30>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	15 <BR CLEAR="all">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	16 Back to <A HREF="index.html">Index</A>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	17 </P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	18 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	19 WIDTH=1010 HEIGHT=2 >
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 <BR CLEAR="all">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	22
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	23
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	24 <H1 ALIGN="LEFT">Introduction to Syntax Directed Parsing</H1>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	25 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	26 WIDTH=1010 HEIGHT=2 >
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	27 </P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	28
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	29 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	30 (Adapted from Chapter 4, AnaGram User's Guide)</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	31 </P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	32 <UL>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	33 <LI SRC="#What"><A HREF="#What">What is Syntax Directed Parsing?</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	34 <LI><A HREF="#Describing">Describing an Input Sequence</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	35 <LI><A HREF="#How">How a Parser Works</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	36 <LI><A HREF="#Note">A Note on Notation</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	37 <LI><A HREF="#Reduction">Reduction Procedures</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	38 <LI><A HREF="#Building">Building a Parser</A>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	39 <UL>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	40 <LI SRC="#Invoking"><A HREF="#Invoking">Invoking a Parser</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	41 <LI><A HREF="#Communicating">Communicating with a Parser</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	42 <LI><A HREF="#Parser">Parser Input</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	43 <LI><A HREF="#Error">Error Handling</A></LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	44 </UL>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	45 </LI>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	46 </UL>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	47 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	48
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	49 <H2><A NAME="What">What is Syntax Directed Parsing?</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	50 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	51 Every programmer has to deal with input data. Usually processing input data
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	52 depends on what has preceded, and often even on what follows, the input under
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	53 consideration. Keeping track of these dependencies in order to know how to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	54 process the data is called parsing. It is often relatively easy to keep track of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	55 simple dependencies when first writing a program. As the program develops, as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	56 new features are added, as bugs are fixed, the dependencies often stop being
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	57 simple. Input processing becomes a headache, since it is hard to keep track of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	58 or even identify all the particular cases. Changes to the program cause
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	59 unexpected problems and program maintenance threatens to get out of control.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	60 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	61 Syntax directed parsing is a technique for addressing these difficulties. In
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	62 syntax directed parsing, the input part of a program is constructed
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	63 automatically, by means of a standard algorithm, from a high level description
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	64 of the input data structure. Code to perform any required processing of the data
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	65 is attached to the description in a convenient way.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	66 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	67 The description, being non-procedural, is generally easier to write and to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	68 modify than the equivalent program code, and much less likely to harbor bugs. It
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	69 is easier to read, and easier to maintain. It is easy to re-use in other
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	70 programs requiring the same input, thus encouraging uniform interfaces. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	71 technique also simplifies the overall program by decoupling the input and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	72 processing components and providing a natural, modular structure.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	73 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	74 To use syntax directed parsing you first write the input data description,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	75 called a <A HREF="gloss.html#Grammar">grammar</A>. A file which contains a grammar is called a syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	76 file. A parser generator, such as AnaGram, then can create, from the syntax
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	77 file, a function (or program) called a <A HREF="gloss.html#Parser">parser</A>, written in C or C++. The parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	78 keeps track of all the dependencies in your input, and calls certain functions,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	79 <A HREF="gloss.html#ReductionProcedure">reduction procedures</A>, to deal with specific units or sequences of data as they
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	80 are encountered.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	81 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	82 Reduction procedures are the code you write to process your data. In your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	83 grammar they are linked to the structures in your input, so that your parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	84 will call them at precisely the right times with precisely the right data. Note
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	85 that with this technique you need only provide a non-procedural <I>description</I>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	86 of the input. The details of flow of control are handled entirely by the parser.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	87 When you write reduction procedures, you can concentrate entirely on what you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	88 have to do with the data. You don't have to encumber your code with switches and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	89 tests to determine the structure of your input.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	90 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	91 The parsers you build using a parser generator such as AnaGram may be complete
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	92 stand-alone programs, or they may serve as input routines for a more extensive
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	93 program. Some programs may even use more than one parser.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	94 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	95
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	96 <H2><A NAME="Describing">Describing an Input Sequence</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	97 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	98 Writing a grammar consists of describing the acceptable input sequences for your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	99 program. The vehicle for describing an input sequence is called a <A HREF="gloss.html#Production">production</A>.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	100 Productions show how a logical component of the input can be made up of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	101 sequence of more elementary components. A production that describes a date might
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	102 be written:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	103 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	104 date
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	105 -> name of month, day, comma, year </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	106 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	107 The components of the input are called <A HREF="gloss.html#Token">tokens</A>. The sequence of tokens on the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	108 side of the production is called a <A HREF="gloss.html#GrammarRule">grammar rule</A>, or rule for short. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	109 individual tokens on the right side of the rule are also called <A HREF="gloss.html#RuleElement">rule elements</A>.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	110 </P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	111 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	112 The token on the left side of the production is called the <A HREF="gloss.html#ReductionToken">reduction token</A> for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	113 the rule. Tokens may have semantic values, as distinguished from syntactic
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	114 values, which you can use in your <A HREF="gloss.html#ReductionProcedure">reduction procedures</A>. For instance, the value
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	115 of name of month could be an integer in the range zero to eleven, or it could be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	116 a pointer to an ascii string. The value of day could be an integer in the range
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	117 one to thirty-one.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	118 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	119 A <A HREF="gloss.html#Grammar">grammar</A> consists of a number of such <A HREF="gloss.html#Production">productions</A>, each of which describes some
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	120 component of the input in terms of other components. It does not take very many
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	121 productions to describe quite complex input streams. A grammar for the C
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	122 language, for instance, requires about two hundred productions.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	123 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	124 Many people find the term "production" quite confusing. It comes from theoretical
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	125 linguistics where it is used to describe how one may produce sequences which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	126 correspond to a set of grammatical rules. Ironically, the major usage of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	127 idea has been in parsing where the interest is not so much in creating sequences
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	128 which satisfy the grammatical rules as in decoding and analyzing such sequences.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	129 Nonetheless, it is convenient, in the above example, to say that the token date
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	130 produces a sequence of tokens consisting of name of month, day, comma, and year.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	131 We also say that the sequence reduces to date.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	132 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	133 There may be more than one production to describe a given component, if there is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	134 more than one way it may be represented. For instance,</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	135 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	136 date
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	137 -> day, name of month, year </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	138 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	139 describes another common way of writing a date. In other words, a <A HREF="gloss.html#ReductionToken">reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	140 token</A> may produce a number of different <A HREF="gloss.html#GrammarRule">grammar rules</A>.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	141 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	142 Tokens which appear on the left side of one or more productions are called
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	143 <A HREF="gloss.html#Nonterminal">nonterminal tokens</A>. Those which appear <I>only</I> on the right sides of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	144 productions are called <A HREF="gloss.html#Terminal">terminal tokens</A>. Terminal tokens are the units which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	145 actually appear physically in the input. Nonterminal tokens are identified when
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	146 a sequence of tokens that matches the right side of a production is seen in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	147 input. When AnaGram analyzes a <A HREF="gloss.html#Grammar">grammar</A>, it assigns a unique token number to each
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	148 token it finds in the grammar.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	149 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	150 Nonterminal tokens, such as date in the example above, may appear in any grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	151 rule just as though they were input tokens. The token on the left side of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	152 production can even appear on the right side as well. Such a production is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	153 called a recursive production. When a nonterminal token appears on the right
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	154 side of a production, it may be represented in this context by <I>any</I> of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	155 the <A HREF="gloss.html#GrammarRule">grammar rules</A> it produces. Grammars described in this manner are called
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	156 <A HREF="gloss.html#ContextFreeGrammar">context free grammars</A> since there is no contextual constraint on which of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	157 rules that a token produces can appear in any given context.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	158 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	159 Recursive productions may be either left recursive or right recursive. Left
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	160 recursive productions are those where the recursively defined <A HREF="gloss.html#Nonterminal">nonterminal</A>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	161 appears as the first <A HREF="gloss.html#RuleElement">element</A> in the recursive rule. Right recursive productions
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	162 are those where it is the last element. If it appears anywhere between, the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	163 production is said to be center recursive.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	164 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	165 Any nonterminal token which has a recursive production must also have at least
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	166 one simple, non-recursive production. Otherwise, it is not possible to create a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	167 finite sequence of terminal tokens from the nonterminal token.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	168 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	169 Recursion may also occur implicitly in a <A HREF="gloss.html#Grammar">grammar</A> when one of the tokens on the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	170 right side of a production itself has a production involving the token on the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	171 left. Such implicit recursion sometimes may involve numerous levels of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	172 productions. Implicit recursion occurs most commonly in describing constructs
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	173 such as arithmetic expressions or the block structure of programming languages.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	174 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	175 Clearly, grammars can accommodate multiple levels of structure in the input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	176 sequences they describe. There must, at the top, be a single token which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	177 encompasses the entire input. This special token is variously called the <A HREF="gloss.html#GrammarToken">grammar
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	178 token</A>, the goal token or the start token.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	179 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	180 AnaGram allows you to specify <A HREF="gloss.html#Terminal">terminal tokens</A> explicitly as ascii characters, or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	181 even as <A HREF="gloss.html#CharacterSets">sets of ascii characters</A>, right in the grammar. Thus, you may write
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	182 '0-9' to represent the set of ascii digits, or 'A-Z' to represent the set of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	183 upper case letters. The semantic value of such a <A HREF="gloss.html#Token">token</A> is the ascii character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	184 code that actually appears in the input stream. If the various sets you use in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	185 your grammar overlap, they may not properly represent terminal tokens. In this
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	186 case, AnaGram automatically extends your <A HREF="gloss.html#Grammar">grammar</A> appropriately. </P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	187 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	188
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	189 <H2><A NAME="How">How a Parser Works</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	190 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	191 The aim of a <A HREF="gloss.html#Parser">parser</A> is to match its input with the full syntactic structure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	192 specified by the <A HREF="gloss.html#Production">productions</A> which make up the grammar. The primary component of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	193 a parser is an input buffer, sometimes thought of as a stack, into which tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	194 are shifted, or stored sequentially, as they are encountered in the input. At
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	195 the same time that a token is shifted into the input buffer, its semantic value
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	196 is pushed onto the value stack. A token is not shifted into the buffer unless it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	197 "makes sense", that is, unless it is consistent with the rules of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	198 <A HREF="gloss.html#Grammar">grammar</A> and with the input that has preceded it. If a token does not make sense,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	199 the parser signals a syntax error. In order to determine whether a token makes
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	200 sense, the parser has a sort of decision table which provides a list of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	201 acceptable tokens for each of a number of states. The table also specifies what
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	202 the parser is to do with each acceptable token. When the table indicates that a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	203 token is to be shifted into the buffer, it also specifies a new state. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	204 parser stacks the current state on a state stack and jumps to the new state.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	205 Thus every time a token is shifted into the input buffer, a state number is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	206 pushed onto the state stack. For each state of the parser, excepting only the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	207 initial state, there is a unique token which will cause a jump to that state.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	208 This token is called the <A HREF="gloss.html#CharacteristicToken">characteristic token</A> for the state.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	209 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	210 When the rightmost, or most recent, tokens in the input buffer match the right
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	211 side of a production precisely, the parser <I>may</I> replace the tokens that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	212 match the rule with a single token, the token on the left side of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	213 production. This process of replacing a sequence of tokens with a single token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	214 is called reduction. The token that replaces the sequence of tokens is called
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	215 the <A HREF="gloss.html#ReductionToken">reduction token</A>.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	216 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	217 The actual mechanism of the reduction is quite important. At the same time that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	218 input tokens are removed from the input buffer, state numbers are popped from
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	219 the state stack, so that when all input tokens matching the rule have been
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	220 removed, the parser state has been restored to the value it had at the time the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	221 first token in the rule was seen. As state numbers are popped from the state
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	222 stack, token values are popped from the value stack. If the rule has a <A HREF="gloss.html#ReductionProcedure">reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	223 procedure</A>, temporary variables are loaded with the values popped from the stack
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	224 and the reduction procedure is called. The reduction token is now shifted into
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	225 the input buffer just as though it were an input token. If the reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	226 procedure returned a result it is shifted into the value stack as the value of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	227 the reduction token. The parser stacks the current state again and jumps to a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	228 new state as determined by the parser tables.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	229 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	230 If there are no errors in your input, when the last token has been read from the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	231 input, shifted into the input buffer, and reductions performed, there will be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	232 precisely one token in the input buffer: the <A HREF="gloss.html#GrammarToken">grammar, or goal, token</A> which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	233 describes your entire input. At this point your parser declares itself finished.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	234 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	235 Reductions do not necessarily occur every time a rule matches the tokens in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	236 input buffer. If the reduction token does not make sense, that is, if it is not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	237 consistent with the rules of the <A HREF="gloss.html#GrammarToken">grammar</A> and with the input that has preceded
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	238 it, the parser will not perform the reduction. Suppose there are tokens in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	239 input which match one of the rules given above for date. A reduction will not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	240 occur unless date is one of the tokens the parser is actually looking for at
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	241 that stage in the input.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	242 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	243 Even when the reduction token would make sense, there are still situations where
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	244 the reduction would not take place. Suppose a grammar includes the two
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	245 <A HREF="gloss.html#Production">productions</A> given above for date as well as the following:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	246 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	247
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	248 date
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	249 -> name of month, day </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	250 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	251 This production is the same as the first, but with no year specification. When a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	252 parser directed by this grammar has encountered name of month and day, it can't
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	253 tell without looking further whether it has a short form or a long form date. In
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	254 such a circumstance, the parser looks at the next following token, which is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	255 called a <A HREF="gloss.html#Lookahead">lookahead token</A>. If the lookahead token is a comma, then, in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	256 absence of other productions, the input is a long form date. If the lookahead
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	257 token is not a comma, then the input is certainly not a long form date, and it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	258 is proper to reduce the short form production.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	259 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	260 Suppose the lookahead token were a comma and the grammar were also to contain
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	261 the following production:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	262 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	263
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	264 appointment
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	265 -> date, comma, time </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	266 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	267 Since a comma can follow date, according to this rule, and can also follow day
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	268 according to the first production, it is impossible to determine, simply by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	269 looking at the <A HREF="gloss.html#Lookahead">lookahead token</A>, whether the date was being given in short form
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	270 or long form. One would have to look beyond the comma to see if what follows the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	271 comma matches the rules for time or for year. Although it is possible to build
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	272 parsers which can do this, it is not generally feasible. Situations of this sort
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	273 are called <A HREF="gloss.html#Conflict">conflicts</A>. AnaGram warns you about the conflicts in your <A HREF="gloss.html#Grammar">grammar</A> when
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	274 it analyzes your grammar, and provides numerous facilities to help you correct
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	275 them.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	276 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	277
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	278 <H2><A NAME="Note">A Note on Notation</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	279 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	280 <A HREF="gloss.html#ContextFreeGrammar">Context free grammars</A> have been traditionally represented in the literature
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	281 using <A HREF="gloss.html#BNF">Backus-Naur Form</A>, or BNF. In Backus-Naur Form, certain characters, called
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	282 metacharacters, are used to punctuate <A HREF="gloss.html#Production">productions</A> and all other printable
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	283 characters are taken to represent themselves literally. Named tokens are denoted
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	284 by enclosing the name within angle brackets <CODE>< ></CODE> . The left side of a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	285 production is distinguished from the right side by the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	286 characters <CODE> ::= </CODE>.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	287 If several productions have the same left side, the vertical
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	288 bar <CODE> \| </CODE> is used to separate them. The <A HREF="gloss.html#RuleElement">elements</A> of a <A HREF="gloss
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	289 .html#GrammarRule">grammar rule</A> are simply juxtaposed
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	290 to indicate that one follows another. Blanks are ignored. Thus, in BNF, the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	291 first production given for date, above, would be:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	292 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	293 <date> ::= <name of month> <day>, <year>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	294 </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	295 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	296 AnaGram uses a notation more consonant with ordinary programming usage. Thus
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	297 token names need not be bracketed and literal characters must be appropriately
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	298 quoted. The elements of rules are joined by commas. Using this approach, there
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	299 is no need for metacharacters and it becomes possible to make a number of useful
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	300 extensions to the notation.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	301 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	302
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	303 <H2><A NAME="Reduction">Reduction Procedures</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	304 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	305 Of course, the reason for parsing an input stream is to interpret the data in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	306 the stream and to process it in some useful manner. The primary tool for doing
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	307 this is the <A HREF="gloss.html#ReductionProcedure">reduction procedure</A>. A reduction procedure is a piece of C code that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	308 is executed when a particular <A HREF="gloss.html#GrammarRule">grammar rule</A> is reduced. Often, a reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	309 procedure calculates a value which becomes the semantic value of the reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	310 token. The input to the reduction procedure consists of the values of the tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	311 that make up the grammar rule.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	312 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	313 AnaGram allows you to assign C variable names to the tokens in a grammar rule,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	314 so that you can refer to them in the reduction procedure. To assign a C variable
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	315 name, simply follow the token in the rule with a colon and the C variable name.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	316 Simple reduction procedures can be written as C or C++ expressions. At the end
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	317 of the rule, write an equal sign and an expression, terminated by a semicolon.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	318 For example:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	319 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	320 (int) hex digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	321 -> '0-9':d =d-'0';
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	322 -> 'a-f':d =d-'a'+10;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	323 -> 'A-F':d =d-'A'+10; </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	324 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	325 When any one of these rules is matched, the value of the token in the rule is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	326 assigned to the temporary variable. The expression to the right of the equal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	327 sign is evaluated and the value of the expression is stored as the value of hex
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	328 digit, which has been declared to be an int. These <A HREF="gloss.html#Production">productions</A> define
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	329 hexadecimal digits as ascii characters, and calculate the binary value of the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	330 digit in terms of the ascii character code, d. The binary value becomes the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	331 value of hex digit. Hexadecimal digits can be combined to make hexadecimal
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	332 numbers by writing the following productions:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	333 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	334 (int) hex number
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	335 -> hex digit
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	336 -> hex number:n, hex digit:d =16*n+d; </PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	337 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	338 There are several important points to notice in this example. First, <A HREF="gloss.html#ReductionProcedure">reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	339 procedures</A> are executed "from the bottom up". That is, the reduction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	340 procedure for hex digit is executed before any reduction procedure for hex
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	341 number. Second, if there is no reduction procedure for a production, the value
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	342 of the first token in the rule is assigned to the reduction token. Thus, it is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	343 not necessary to provide a reduction procedure in the first production for hex
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	344 number. Third, the reduction procedures for recursive productions are always
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	345 executed <I>after</I> the reduction procedure, if any, for the non-recursive
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	346 production which begins the recursion. Finally, when an input sequence is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	347 described using left recursion, as in this example, the <A HREF="gloss.html#RuleElement">elements</A> of the sequence
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	348 are processed left to right.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	349 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	350 If you wish to process the elements of a sequence right to left, you may use
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	351 right recursion. For example, it is sometimes convenient to define the fraction
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	352 part of a decimal number thus:</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	353 <PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	354 (double) fraction part
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	355 -> '0-9':d =(d-'0')/10.;
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	356 -> '0-9':d,fraction part:f =(d-'0'+f)/10.;</PRE>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	357 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	358 In this case the leading digits are stored temporarily in the parse stack, and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	359 then the fraction part is evaluated right to left only when the last digit has
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	360 been found.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	361 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	362 Reduction procedures can be more complex than simple expressions. After the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	363 equal sign you may include an arbitrary block of C or C++ code, enclosed in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	364 braces, { }. To return a semantic value for the reduction token simply use a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	365 return statement. Of course, reduction procedures have the full resources of C
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	366 or C++ at their disposal. They may set and interrogate global variables and may
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	367 call functions freely.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	368 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	369 Since the reduction procedures you write will probably need some support code,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	370 such as #include statements and declarations, you may incorporate C or C++ code
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	371 into your syntax file at any point. You need only enclose it in braces ({}).
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	372 Such code is called embedded C. All embedded C code is also copied to the parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	373 file, and <I>precedes</I> all of your reduction procedures.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	374 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	375
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	376 <H2><A NAME="Building">Building a Parser</A></H2>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	377 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	378 In order to round out a <A HREF="gloss.html#Parser">parser</A> into a functioning program it needs input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	379 procedures, as well as error diagnosis and recovery capabilities. AnaGram has a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	380 number of options available which give you a high degree of flexibility in
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	381 configuring a parser to suit your particular needs. All of the options are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	382 provided with reasonable defaults, so that you can safely disregard any option
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	383 until you need the features it provides.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	384 <BR>
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 <H4><A NAME="Invoking">Invoking a Parser</A></H4>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	387 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	388 Normally, AnaGram configures <A HREF="gloss.html#Parser">parsers</A> as functions which you can call from
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	389 elsewhere in your program. In this situation, you call the parser, it processes
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	390 its input, and returns either when it has finished or cannot proceed because of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	391 errors. Alternatively, if you set the event driven configuration switch, your
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	392 parser will be configured so that you have two procedures to call: an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	393 initializer and a parser. In the event driven configuration you start the parse
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	394 by calling the initializer and then you call the parser once for each unit of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	395 input. Using the event driven mode makes it quite easy to configure a parser as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	396 a filter and to chain several parsers together so that the output from one
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	397 parser is the input to the next. Such multi-stage parsing is a convenient way to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	398 deal with complex input that is not context free.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	399 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	400
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	401 <H4><A NAME="Communicating">Communicating with a Parser</A></H4>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	402 <P>The complete status of your parser is contained in a single data structure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	403 called a parser control block. All communications with a parser take place via
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	404 the parser control block. Input procedures must place input data in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	405 appropriate field in the parser control block. When the parse is complete or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	406 encounters an error, the results of the parse may be found in the parser control
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	407 block. When AnaGram builds a parser it includes, in the header file it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	408 generates, a typedef statement which defines the structure of the parser control
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	409 block.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	410 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	411
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	412 <H4><A NAME="Parser">Parser Input</A></H4>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	413 <P>The input to your <A HREF="gloss.html#Parser">parser</A> may be either characters read directly from an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	414 input stream, or tokens accumulated by a pre-processor or <A HREF="gloss.html#LexicalScanner">lexical scanner</A>. The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	415 way you provide input to your parser depends on how your <A HREF="gloss.html#Grammar">grammar</A> defines input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	416 tokens and also on whether or not you have requested an event driven parser.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	417 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	418 If your parser is event driven, you provide its input by storing the input code
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	419 and the input value, if any, into the parser control block and calling the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	420 parser.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	421 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	422 If you have set the pointer input configuration switch in your syntax file, you
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	423 simply initialize the pointer field in your parser control block before you call
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	424 your parser. Your parser will then read its input directly from memory by simply
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	425 incrementing the pointer as necessary.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	426 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	427 Otherwise, your parser will invoke a macro called GET_INPUT every time it needs
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	428 more input. You may define GET_INPUT according to your needs. You can define it
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	429 so that it calls an input function, or you can define it so that it executes
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	430 in-line code each time it is invoked. Your GET_INPUT macro should store its
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	431 input code in the input_code field of the parser control block. If you do not
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	432 write a GET_ INPUT macro, AnaGram will provide one which will read characters
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	433 from stdin.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	434 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	435 If your <A HREF="gloss.html#Grammar">grammar</A> does not define <A HREF="gloss.html#Terminal">terminal tokens</A> in terms of ascii characters or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	436 external token numbers, your GET_INPUT will have to determine the appropriate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	437 internal token number for each input token. To assist you in determining these
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	438 token numbers AnaGram provides a typedef enum statement in the header file. You
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	439 can then use named constants to specify the internal token numbers for the input
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	440 tokens.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	441 <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	442
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	443 <H4><A NAME="Error">Error Handling</A></H4>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	444 <P>Your <A HREF="gloss.html#Parser">parser</A> must be prepared to deal with erroneous input. There are two
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	445 aspects to error handling: diagnosing the error, and recovering from the error.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	446 On encountering an error, your parser will invoke a macro called SYNTAX_ ERROR.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	447 If you do not provide a definition for SYNTAX_ERROR, AnaGram will provide a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	448 simple error diagnostic. AnaGram can also provide automatic error diagnoses
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	449 which pinpoint the location of the error.</P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	450 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	451 AnaGram provides two options for error recovery: error
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	452 token <A HREF="gloss.html#Resynchronization">resynchronization</A>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	453 and automatic resynchronization. These are techniques for getting your parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	454 back in synch with its input so it can proceed after encountering an error.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	455 Normally, if you do not select one of these recovery techniques, your parser
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	456 will terminate when it encounters an error; however, you may override this
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	457 default if you wish and provide your own recovery technique.</P>
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
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	460 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	461 WIDTH=1010 HEIGHT=2 >
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	462 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	463 <IMG ALIGN="right" SRC="images/pslrb6d.gif" ALT="Parsifal Software"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	464 WIDTH=181 HEIGHT=25>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	465 <BR CLEAR="right">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	466
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	467 Back to <A HREF="index.html">Index</A>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	468 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	469 <ADDRESS><FONT SIZE="-1">
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	470 AnaGram parser generator - documentation<BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	471 Introduction to Syntax Directed Parsing<BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	472 Copyright © 1993-1999, Parsifal Software. <BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	473 All Rights Reserved.<BR>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	474 </FONT></ADDRESS>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	475
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	476 </BODY>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	477 </HTML>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	478
13d2b8934445 Import AnaGram (near-)release tree into Mercurial. David A. Holland parents: diff changeset	479

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