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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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2 <HTML>
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3 <HEAD>
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4 <TITLE> Token Scanner - Macro preprocessor and C Parser </TITLE>
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5 </HEAD>
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6
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7 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
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8 TEXT="#000000" LINK="#0033CC"
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9 VLINK="#CC0033" ALINK="#CC0099">
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10
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11 <P>
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12 <IMG ALIGN="right" SRC="../../images/agrsl6c.gif" ALT="AnaGram"
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13 WIDTH=124 HEIGHT=30 >
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14 <BR CLEAR="all">
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15 Back to :
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16 <A HREF="../../index.html">Index</A> |
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17 <A HREF="index.html">Macro preprocessor overview</A>
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18 <P>
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19 <IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
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20 WIDTH=1010 HEIGHT=2 >
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21 <P>
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22
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23 <H1> Token Scanner - Macro preprocessor and C Parser </H1>
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24 <IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
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25 WIDTH=1010 HEIGHT=2 >
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26 <P>
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27 <BR>
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28
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29 <H2>Introduction</H2>
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30
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31 The token scanner module, <tt>ts.syn</tt>, accomplishes the following
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32 tasks:
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33 <OL>
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34 <LI> It reads the raw input, gathers tokens and identifies
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35 them. </LI>
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36 <LI> It analyzes conditional compilation directives and
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37 skips over text that is to be omitted. </LI>
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38 <LI> It analyzes macro definitions and maintains the macro
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39 tables. </LI>
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40 <LI> It identifies macro calls in the input stream and calls
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41 the <tt>macro_expand()</tt> function to expand them. </LI>
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42 <LI> It recognizes <tt>#include</tt> statements and calls itself
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43 recursively to parse the include file. </LI>
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44 </OL>
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45
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46 The token_scanner parser, <tt>ts()</tt>, is called from a shell
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47 function, <tt>scan_input(char *)</tt>, which takes the name
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48 of a file
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49 as an argument. <tt>scan_input()</tt> opens the file, calls
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50 <tt>ts()</tt>, and
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51 closes the file. <tt>scan_input()</tt> is called recursively by
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52 <tt>include_file()</tt> when an <tt>#include</tt> statement
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53 is found in the
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54 input.
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55 <P>
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56 Output from the token scanner is directed to a token_sink
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57 pointed to by the <tt>scanner_sink</tt> global variable. The main
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58 program may set scanner sink to point to either a
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59 <tt>token_translator</tt> or a <tt>c_parser</tt>. During the
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60 course of
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61 processing, the token scanner redirects output to a token
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62 accumulator or to the conditional expression evaluator, as
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63 necessary, by temporarily changing the value of
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64 <tt>scanner_sink</tt>.
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65 <P>
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66 The token scanner module contains two syntax error
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67 diagnostic procedures: <tt>syntax_error(char *)</tt> and
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68 <tt>syntax_error_scanning(char *)</tt>. The former is set up to
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69 provide correct line and column numbers for functions called
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70 from reduction procedures in the token scanner. The latter
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71 is set up to provide line and column numbers for errors
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72 discovered in the scanner itself. Both functions accept a
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73 pointer to an error message.
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74 <P>
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75 <BR>
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76
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77 <H2> Theory of Operation </H2>
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78
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79 The primary purpose of the token scanner is to identify the
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80 C language tokens in the input file and pass them on to
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81 another module for further processing. In order to package
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82 them for transmission, the token scanner maintains a "token
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83 dictionary", <tt>td</tt>, which enables it to characterize each
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84 distinct input token with a single number. The token scanner
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85 also classifies tokens according to the definitions of the C
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86 language. The "token" that it passes on for further
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87 processing is a pair consisting of an id field, and a value
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88 field. The id field is defined by the <tt>token_id</tt>
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89 enumeration
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90 in <tt>token.h</tt>. The value field is the index of the
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91 token in the
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92 token dictionary, <tt>td</tt>.
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93 <P>
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94 To support its primary purpose, the token scanner deals with
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95 several other problems. First, it identifies preprocessor
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96 control lines which control conditional compilation and
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97 skips input appropriately. Second, it fields <tt>#include</tt>
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98 statements, and recurses to process include files. Third, it
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99 fields <tt>#define</tt> statements and manages the macro definition
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100 tables. Finally, it checks the tokens it identifies and
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101 calls the macro/argument expansion module to expand them if
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102 they turn out to be macros.
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103 <P>
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104 The conditional compilation logic in the token scanner is
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105 carried out in its entirety by syntactic means. The only C
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106 code involved deals with evaluating conditional statements.
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107 <tt>#ifdef</tt> and <tt>#ifndef</tt> are quite
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108 straightforward. <tt>#if</tt> is another
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109 matter. To deal with the generality of this statement, token
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110 scanner output is diverted to the expression evaluator
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111 module, <tt>ex.syn</tt>, where the expression is evaluated. The
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112 outcome of the calculation is then used to control a
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113 semantically determined production in the token scanner.
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114 <P>
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115 Processing <tt>#include</tt> statements is reasonably
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116 straightforward. Token scanner output is diverted to the
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117 token accumulator, <tt>ta</tt>. The content of the token accumulator
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118 is then translated back to ASCII string form. This takes
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119 care of macro calls in the <tt>#include</tt> statement. Once the file
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120 has been identified, <tt>scan_input()</tt> is called recursively to
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121 deal with it.
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122 <P>
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123 The only complication with macro definitions is that the
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124 tokens which comprise the body of a macro must not be
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125 expanded until the macro is invoked. For that reason, there
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126 are two different definitions of token in the token scanner:
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127 "simple token" and "expanded token". The difference is that
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128 simple tokens are not checked for macro calls. When a macro
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129 definition is encountered, the token scanner output is
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130 diverted to the token accumulator, so that the body of the
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131 macro can be captured and stored.
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132 <P>
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133 When a macro call is recognized, the token scanner must pick
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134 up the arguments for the macro. There are three
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135 complications here: First, the tokens must not be scanned
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136 for macros; second, the scan must distinguish the commas
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137 that separate arguments from commas that may be contained
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138 inside balanced parentheses within an argument; and finally,
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139 leading white space tokens do not count as argument tokens.
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140 <P>
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141 <BR>
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142
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143 <H2> Elements of the Token Scanner </H2>
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144
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145 The remainder of this document describes the macro
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146 definitions, the structure definitions, the static data
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147 definitions, all configuration parameter settings, and all
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148 non-terminal parsing tokens used in the token scanner. It
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149 also explains each configuration parameter setting in the
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150 syntax file. In <tt>ts.syn</tt>, each function that is defined is
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151 preceded by a short explanation of its purpose.
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152 <P>
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153 <BR>
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154
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155 <H2> Macro definitions </H2>
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156 <DL>
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157 <DT> <tt>GET_CONTEXT</tt>
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158 <DD> The <tt>GET_CONTEXT</tt> macro provides the parser with context
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159 information for the input character. (Instead of writing a
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160 <tt>GET_CONTEXT</tt> macro, the context information could be stored
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161 as part of <tt>GET_INPUT</tt>.)
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162
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163 <DT> <tt>GET_INPUT</tt>
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164 <DD> The <tt>GET_INPUT</tt> macro provides the next input
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165 character for
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166 the parser. If the parser used <b>pointer input</b> or <b>event
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167 driven</b> input, a <tt>GET_INPUT</tt> macro would not be
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168 necessary. The
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169 default for <tt>GET_INPUT</tt> would read <tt>stdin</tt> and
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170 so is not
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171 satisfactory for this parser.
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172
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173 <DT> <tt>PCB</tt>
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174 <DD> Since the <b>declare pcb</b> switch has been turned off, AnaGram
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175 will not define <tt>PCB</tt>. Making the parser control block part of
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176 the file descriptor structure simplifies saving and
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177 restoring the pcb for nested #include files.
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178
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179 <DT> <tt>SYNTAX_ERROR</tt>
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180 <DD> <tt>ts.syn</tt> defines the <tt>SYNTAX_ERROR</tt> macro,
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181 since otherwise the
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182 generated parser would use the default definition of
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183 <tt>SYNTAX_ERROR</tt>, which would not provide the name of the file
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184 currently being read.
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185 </DL>
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186 <P>
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187 <BR>
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188
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189 <H2> Local Structure Definitions </H2>
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190 <DL><DT> <tt>location</tt>
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191 <DD> <tt>location</tt> is a structure which records a line
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192 number and a
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193 column number. It is handed to AnaGram with the context type
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194 statement found in the configuration segment. AnaGram then
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195 declares two member fields of type <tt>location</tt> in the parser
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196 control block: <tt>input_context</tt> and a stack, <tt>cs</tt>. In
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197 <tt>scan_input()</tt>, the <tt>input_context</tt> variable
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198 is set explicitly
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199 with the current line and column number. In <tt>syntax_error()</tt>
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200 the <tt>CONTEXT</tt> macro is used to extract the line and column
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201 number at which the rule currently being reduced started.
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202
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203 <DT> <tt>file_descriptor</tt>
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204 <DD> <tt>file_descriptor</tt> contains the information that
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205 needs to be
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206 saved and restored when nested include files are processed.
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207 </DL>
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208 <P>
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209 <BR>
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210
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211 <H2> Static Variables </H2>
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212 <DL><DT> <tt>error_modifier</tt>
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213 <DD> Type: <tt>char *</tt><BR>
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214
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215 The string identified by <tt>error_modifier</tt> is added to the
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216 error diagnostic printed by <tt>syntax_error()</tt>. Normally it is
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217 an empty string; however, when macros are being expanded it
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218 is set so that the diagnostic will specify that the error
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219 was found inside a macro expansion.
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220
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221 <DT> <tt>input</tt>
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222 <DD> Type: <tt>file_descriptor</tt><BR>
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223
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224 <tt>input</tt> provides the name and stream pointer for the
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225 currently active
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226 input file.
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227
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228 <DT> <tt>save_sink</tt>
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229 <DD> Type: <tt>stack&lt;token_sink *&gt;</tt><BR>
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230
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231 This stack provides for saving and restoring <tt>scanner_sink</tt>
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232 when it is necessary to divert the scanner output for
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233 dealing with conditional expressions, macro definitions and
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234 macro arguments. Actually, a stack is not necessary, since
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235 such diversions never nest more than one level deep, but it
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236 seems clearer to use a stack.
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237 </DL>
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238 <P>
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239 <BR>
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240
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241 <H2> Configuration Parameters </H2>
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242 <DL><DT> <tt>~allow macros</tt>
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243 <DD> This statement turns off the <b>allow macros</b> switch so that
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244 AnaGram implements all reduction procedures as explicit
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245 function definitions. This simplifies debugging at the cost
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246 of a slight performance degradation.
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247
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248 <DT> <tt>auto resynch</tt>
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249 <DD> This switch turns on automatic resynchronization in case a
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250 syntax error is encountered by the token scanner.
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251
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252 <DT> <tt>context type = location</tt>
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253 <DD> This statement specifies that the generated parser is to
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254 track context automatically. The context variables have type
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255 <tt>location</tt>. <tt>location</tt> is defined elsewhere to
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256 consist of two
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257 fields: line number and column number.
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258
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259 <DT> <tt>~declare pcb</tt>
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260 <DD> This statement tells AnaGram not to declare a parser control
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261 block for the parser. The parser control block is declared
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262 later as part of the <tt>file_descriptor</tt> structure.
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263
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264 <DT> <tt>~error frame</tt>
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265 <DD> This turns off the error frame portion of the automatic
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266 syntax error diagnostic generator, since the context of the
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267 error in the scanner syntax is of little interest. If an
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268 error frame were to be used in diagnostics that of the C
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269 parser would be more appropriate.
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270
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271 <DT> <tt>error trace</tt>
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272 <DD> This turns on the <b>error trace</b> functionality, so
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273 that if the token
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274 scanner encounters a syntax error it will write an <tt>.etr</tt>
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275 file.
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276
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277 <DT> <tt>line numbers</tt>
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278 <DD> This statement causes AnaGram to include <tt>#line</tt>
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279 statements in
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280 the parser file so that your compiler can provided
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281 diagnostics keyed to your syntax file.
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282
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283 <DT> <tt>subgrammar</tt>
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284 <DD> The basic token grammar for C is usually implemented using
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285 some sort of regular expression parser, such as <tt>lex</tt>, which
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286 always looks for the longest match to the regular
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287 expression. In no case does the regular expression parser
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288 use what follows a match to determine the nature of the
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289 match. An LALR parser generator, on the other hand, normally
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290 looks not only at the content of a token but also looks
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291 ahead. The subgrammar declaration tells AnaGram not to look
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292 ahead but to parse these tokens based only on their internal
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293 structure. Thus the conflicts that would normally be
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294 detected are not seen. To see what happens if lookahead is
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295 allowed, simply comment out any one of these subgrammar
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296 statements and look at the conflicts that result.
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297
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298 <DT> <tt>~test range</tt>
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299 <DD> This statement tells AnaGram not to check input characters
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300 to see if they are within allowable limits. This checking is
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301 not necessary since the token scanner is reading a text file
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302 and cannot possibly get an out of range token.
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303 </DL>
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304 <P>
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305 <BR>
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306
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307 <H2> Scanner Tokens, in alphabetical order </H2>
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308 <DL><DT> any text
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309 <DD> These productions are used when skipping over text. "any
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310 text" consists of all characters other than eof, newline and
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311 backslash, as well as any character (including newline and
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312 backslash) that is quoted with a preceding backslash
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313 character.
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314
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315 <DT> arg element
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316 <DD> An "arg element" is a token in the argument list of a macro.
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317 It is essentially the same as "simple token" except that
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318 commas must be detected as separators and nested parentheses
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319 must be recognized. An "arg element" is either a space or an
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David A. Holland
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diff changeset
320 "initial arg element".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
321
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
322 <DT> character constant
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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323 <DD> A "character constant" is a quoted character or escape
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
324 sequence. The token scanner does not inquire closely into
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
325 the internal nature of the character constant.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
326
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
327 <DT> comment
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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328 <DD> A "comment" consists of a comment head followed by the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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329 closing "*/".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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330
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
331 <DT> comment head
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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332 <DD> A "comment head" consists of the entire comment up to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
333 closing "*/". If a complete comment is found following a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
334 comment head, its treatment depends on whether one believes,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
335 with ANSI, that comments should not be nested, or whether
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
336 one prefers to allow nested comments. Followers of the ANSI
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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337 principle will want "comment head, comment" to reduce to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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338 "comment". Believers in nested comments will want to finish
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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339 the comment that was in progress when the nested comment was
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
340 encountered, so they will want "comment head, comment" to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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341 reduce to "comment head", which will allow the search for
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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342 "*/" to continue.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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343
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344 <DT> conditional block
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345 <DD> A "conditional block" is an #if, #ifdef, or #ifndef line and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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346 all following lines through the terminating #endif. If the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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347 initial condition turns out to be true, then everything has
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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348 to be skipped following an #elif or #else line. If the
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349 initial condition is false, everything has to be skipped
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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350 until a true #elif condition or an #else line is found.
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351
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352 <DT> confusion
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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353 <DD> This token is designed to deal with a curious anomaly of C.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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354 Integers which begin with a zero are octal, but floating
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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355 point numbers may have leading zeroes without losing their
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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356 fundamental decimal nature. "confusion" is an octal integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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357 that is followed by an eight or a nine. This will become
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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358 legitimate if eventually a decimal point or an exponent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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359 field is encountered.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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360
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
361 <DT> control line
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362 <DD> "control line" consists of any preprocessor control line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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363 other than those associated with conditional compilation.
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364
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
365 <DT> decimal constant
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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366 <DD> A "decimal constant" is a "decimal integer" and any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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367 following qualifiers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
368
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
369 <DT> decimal integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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370 <DD> The digits which comprise the integer are pushed onto the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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371 string accumulator. When the integer is complete, the string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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372 will be entered into the token dictionary and subsequently
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
373 it will be described by its index in the token dictionary.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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374
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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375 <DT> defined
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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376 <DD> See "expanded word". id_macro will recognize "defined" only
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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377 when the if_clause switch is set.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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378
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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379 <DT> eof
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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380 <DD> end of file: equal to the null character.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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381
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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382 <DT> eol
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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383 <DD> end of line: a newline and all immediately following white
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
384 space or newline characters. eol is declared to be a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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385 subgrammar since it is used in circumstances where space can
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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386 legitimately follow, according to the syntax as written.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
387
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
388 <DT> else if header
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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389 <DD> This production is simply a portion of the rule for the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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390 #elif statement. It is separated out in order to provide a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
391 hook on which to hang the call to init_condition(), which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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392 diverts scanner output to the expression_evaluator which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
393 will calculate the value of the conditional expression.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
394
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
395 <DT> else section
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
396 <DD> An "else section" is an #else line and all immediately
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
397 following complete sections. An "else section" and a "skip
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
398 else section" are the same except that in an "else section"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
399 tokens are sent to the scanner output and in a "skip else
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
400 section" they are discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
401
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
402 <DT> endif line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
403 <DD> An "endif line" is simply a line that begins #endif
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
404
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
405 <DT> expanded token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
406 <DD> The word "token" is used here in the sense of Kernighan and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
407 Ritchie, 2nd Edition, Appendix A, p. 191. In this program a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
408 "simple token" is one which is simply passed on without
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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diff changeset
409 regard to macro processing. An "expanded token" is one which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
410 has been checked to see if it is a macro identifier and, if
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
411 so, expanded. "simple tokens" are recognized only in the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
412 bodies of macro definitions. Therefore spaces and '#'
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
413 characters are passed on. For "expanded tokens" they are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
414 discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
415
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
416 <DT> expanded word
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
417 <DD> This is the treatment of a simple identifier as an "expanded
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
418 token". "variable", "simple macro", "macro", and "defined"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
419 are the various outcomes of semantic analysis of "name
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
420 string" performed by id_macro(). In this case reserved words
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
421 and identifiers which are not the names of macros are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
422 subsumed under the rubric "variable". These tokens are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
423 simply passed on to the scanner output.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
424 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
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diff changeset
425 The distinction between "macro" and "simple macro" depends
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
426 on whether the macro was defined with or without following
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
427 parentheses. A "simple macro" is expanded by calling
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
428 expand(). expand() simply serves as a local interface to the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
429 expand_text() function defined in <tt>mas.syn</tt>.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
430 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
431 If a "macro" was defined with parentheses but appears bereft
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
432 of an argument list, it is treated as a simple identifier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
433 and passed on to the output. Otherwise the argument tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
434 for the macro are gathered and stacked on the token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
435 accumulator, using "macro arg list". Finally, the macro is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
436 expanded in the same way as a "simple macro". Note that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
437 "macro arg list" provides a count of the number of arguments
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
438 found inside the balanced parentheses.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
439 <P>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
440 If "if_clause" is set, it means that the conditional
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
441 expression of an #if or #elif line is being evaluated. In
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
442 this case, the pseudo-function defined() must be recognized
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
443 to determine whether a macro has or has not been defined.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
444 The defined() function returns a "1" or "0" token depending
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
445 on whether the macro has been defined.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
446
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
447 <DT> exponent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
448 <DD> This is simply the exponent field on a floating point number
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
449 with optional sign.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
450
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
451
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
452 <DT> false condition
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
453 <DD> The "true condition" and "false condition" tokens are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
454 semantically determined. They consist of #if, #ifdef, or
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
455 #ifndef lines. If the result of the test is true the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
456 reduction token is "true condition", otherwise it is "false
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
457 condition".
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 <DT> false else condition
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
460 <DD> The "true else condition" and "false else condition" tokens
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
461 are semantically determined. They consist of an #elif line.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
462 If the value of the conditional expression is true the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
463 reduction token is "true else condition", otherwise it is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
464 "false else condition".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
465
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
466 <DT> false if section:
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
467 <DD> A "false if section" is a #if, #ifdef, or #ifndef condition
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
468 that turns out to be false followed by any number, including
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
469 zero, of complete sections or false #elif condition lines.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
470 All of the text within a "false if section" is discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
471 <DT> floating qualifier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
472 <DD> These productions are simply the optional qualifiers to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
473 specify that a constant is to be treated as a float or as a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
474 long double.
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 <DT> hex constant
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
477 <DD> A "hex constant" is simply a "hex integer" plus any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
478 following qualifiers.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
479
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
480 <DT> hex integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
481 <DD> The digits which comprise the integer are pushed onto the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
482 string accumulator. When the integer is complete, the string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
483 will be entered into the token dictionary and subsequently
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
484 it will be described by its index in the token dictionary.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
485
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
486 <DT> if header
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
487 <DD> This production is simply a portion of the rule for the #if
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
488 statement. It is separated out in order to provide a hook on
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
489 which to hang the call to init_condition(), which diverts
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
490 scanner output to the expression evaluator which will
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
491 calculate the value of the conditional expression.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
492
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
493 <DT> initial arg element
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
494 <DD> In gathering macro arguments, spaces must not be confused
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
495 with a true argument. Therefore, the arg element token is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
496 broken down into two pieces so that each argument begins
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
497 with a nonblank token.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
498
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
499 <DT> include header
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
500 <DD> "include header" simply represents the initial portion of an
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
501 #include line and provides a hook for a reduction procedure
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
502 which diverts scanner output to the token accumulator. This
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
503 diversion allows the text which follows #include to be
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
504 scanned for macros and accumulated. The include_file()
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
505 function will be called to actually identify and scan the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
506 specified file.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
507
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
508 <DT> input file
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
509 <DD> This is the grammar, or start token. It describes the entire
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
510 file as alternating sections and eols, terminated by an eof
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 <DT> integer constant
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
513 <DD> These productions simply gather together the varieties of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
514 integer constants under one umbrella.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
515
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
516 <DT> integer qualifier
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
517 <DD> These productions are simply the optional qualifiers to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
518 specify that an "integer constant" is to be treated as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
519 unsigned, long, or both.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
520
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
521 <DT> macro
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
522 <DD> See "expanded word". id_macro specifies "macro" or "simple
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
523 macro" depending on whether the named macro was defined with
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
524 or without following parentheses.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
525
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
526 <DT> macro arg list
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
527 <DD> A "macro arg list" can be either empty or can consist of any
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
528 number of token sequences separated by commas. Commas that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
529 are protected by nested parentheses do not separate
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
530 arguments. Argument strings are accumulated on the token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
531 accumulator and counted by "macro args".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
532
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
533 <DT> macro args
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
534 <DD> Each argument to a macro is gathered on a separate level of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
535 the token accumulator, so the token accumulator level is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
536 incremented before each argument, and the arguments are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
537 counted.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
538
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
539 <DT> macro definition header
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
540 <DD> The "macro definition header" consists of the #define line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
541 up to the beginning of the body text of the macro. It serves
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
542 as a hook to call init_macro_def() which begins the macro
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
543 definition and diverts scanner output to the token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
544 accumulator. The macro definition will be completed by the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
545 save_macro_body() function once the entire macro body has
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
546 been accumulated. Note that the tokens for the macro body
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
547 are not examined for macro calls.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
548
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
549 <DT> name string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
550 <DD> "name string" is simply an accumulation on the string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
551 accumulator of the characters which make up an identifier.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
552
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
553 <DT> nested elements
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
554 <DD> "nested elements" are "arg elements" that are found inside
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
555 nested parentheses.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
556
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
557 <DT> not control mark
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
558 <DD> This consists of any input character excepting eof, newline,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
559 backslash and '#', but including any of these if preceded by
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
560 a backslash. It serves, at the beginning of a line, to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
561 distinguish ordinary lines of text from preprocessor control
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
562 lines.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
563 <DT>
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
564 octal integer
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
565 <DD> The digits which comprise the integer are pushed onto the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
566 string accumulator. When the integer is complete, the string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
567 will be entered into the token dictionary and subsequently
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
568 it will be described by its index in the token dictionary.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
569
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
570 <DT> operator
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
571 <DD> This is simply an inventory of all the multi-character
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
572 operators in C.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
573
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
574 <DT> parameter list
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
575 <DD> "parameter list" is simply a wrapper about "names" which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
576 allows for empty parentheses. Note that both the "names"
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
577 token and the "parameter list" tokens provide the count of
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
578 the number of parameter names found inside the parentheses.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
579 The names themselves have been stacked on the string
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
580 accumulator.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
581
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
582 <DT> qualified real
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
583 <DD> This production exists to allow the "floating qualifier" to
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
584 be appended to a "real constant".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
585 <DT> real
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
586 <DD> These productions itemize the various ways of writing a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
587 floating point number with and without decimal points and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
588 with and without exponent fields.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
589
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
590 <DT> real constant
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
591 <DD> This production is simply an envelope to contain "real" and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
592 write the output code once instead of four times.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
593
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
594 <DT> section
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
595 <DD> This is a logical block of input. It is either a single line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
596 of ordinary code, a control line such as #define or #undef,
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
597 or an entire conditional compilation block, i.e., everything
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
598 from the #if to the closing #endif. Notice that the eol that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
599 terminates a "section" is not part of the "section". The
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
600 only difference between a "section" and a "skip section" is
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
601 that in a "section", all tokens are sent to the scanner
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
602 output while in a "skip section", all input is discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
603
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
604 <DT> separator
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
605 <DD> This is simply a gathering together of all the tokens that
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
606 are neither white space nor identifiers, since they are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
607 treated uniformly throughout the grammar.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
608
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
609 <DT> simple macro
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
610 <DD> See "expanded word".
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
611
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
612 <DT> simple real
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
613 <DD> A "simple real" is one which has a decimal point and has
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
614 digits on at least one side of the decimal point.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
615 Unaccompanied decimal points will be turned away at the
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
616 door.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
617 <DT> simple token
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
618 <DD> The word "token" is used here in the sense of Kernighan and
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
619 Ritchie, 2nd Edition, Appendix A, p. 191. In this program a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
620 "simple token" is one which is simply passed on without
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
621 regard to macro processing. An "expanded token" is one which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
622 has been checked to see if it is a
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
623 <P> macro identifier and, if so, expanded. "simple tokens" are
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
624 recognized only in the bodies of macro definitions.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
625 Therefore spaces and '#' characters are passed on. For
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
626 "expanded tokens" they are discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
627
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
628 <DT> skip else line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
629 <DD> For purposes of skipping over complete conditional sections
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
630 #elif and #else lines are equivalent.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
631
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
632 <DT> skip else section
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
633 <DD> A "skip else section" consists of the #else or #elif line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
634 following a satisfied conditional and all subsequent
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
635 sections and #elif and #else lines. All input in the "skip
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
636 else section" is discarded.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
637
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
638 <DT> skip if section
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
639 <DD> A "skip if section" consists of an #if, #ifdef, or #ifndef
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
640 line, and all following complete "sections" (represented as
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
641 "skip sections", so their content will be ignored) and #else
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
642 and #elif lines.
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
643
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
644 <DT> skip line
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
645 <DD> When skipping text, we have to distinguish between lines
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
David A. Holland
parents:
diff changeset
646 which begin with the control mark ('#') and those which
13d2b8934445 Import AnaGram (near-)release tree into Mercurial.
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647 don't so that we deal correctly with nested #endif
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648 statements. We wouldn't want to terminate a block of
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649 uncompiled code with the wrong #endif.
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650
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651 <DT> skip section
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652 <DD> A "skip section" is simply a "section" that follows an
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653 unsatisfied conditional. In a "skip section", all input is
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654 discarded.
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655
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656 <DT> space
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657 <DD> space consists of either a blank or a comment. If a comment
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658 is found, it is replaced with a blank.
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659 <DT> simple chars
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660 <DD> "simple chars" consists of the body of a character constant
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661 up to but not including the final quote.
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662
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663 <DT> string chars
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664 <DD> "string chars" consists of the body of a string literal up
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665 to but not including the final double quote.
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666
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667 <DT> string literal
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668 <DD> A "string literal" is simply a quoted string. It is
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669 accumulated on the string accumulator.
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670
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671 <DT> true condition
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672 <DD> The "true condition" and "false condition" tokens are
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673 semantically determined. They consist of #if, #ifdef, or
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674 #ifndef lines. If the result of the test is true the
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675 reduction token is "true condition", otherwise it is "false
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676 condition".
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677
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678 <DT> true condition
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679 <DD> The "true condition" and "false condition" tokens are
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680 semantically determined. They consist of #if, #ifdef, or
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681 #ifndef lines. If the result of the test is true the
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682 reduction token is "true condition", otherwise it is "false
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683 condition".
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684
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685 <DT> true else condition
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686 <DD> The "true else condition" and "false else condition" tokens
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687 are semantically determined. They consist of an #elif line.
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688 If the value of the conditional expression is true the
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689 reduction token is "true else condition", otherwise it is
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690 "false else condition".
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691
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692 <DT> true if section
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693 <DD> A "true if section" is a true #if, #ifdef, or #ifndef,
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694 followed by any number of complete sections, including zero.
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695 Alternatively, it could be a "false if section" that is
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696 followed by a true #elif condition, followed by any number
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697 of complete "sections". All input in a "true if section"
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698 subsequent to the true condition is passed on to the scanner
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699 output.
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700
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701 <DT> word
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702 <DD> This is the treatment of a simple identifier as a "simple
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703 token". The name_token() procedure is called to pop the name
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704 string from the string accumulator, identify it in the token
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705 dictionary and assign a token_id to it by checking to see if
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706 it is a reserved word.
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707
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708 <DT> variable
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709 <DD> See "expanded word".
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710
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711 ws
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712 <DD> The definition for ws as space... simply allows a briefer
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713 reference in those places in the grammar where it is
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714 necessary to skip over white space.
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715 </DL>
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716 <P>
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717 <BR>
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718
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719
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720 <IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
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721 WIDTH=1010 HEIGHT=2 >
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722 <P>
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723 <IMG ALIGN="right" SRC="../../images/pslrb6d.gif" ALT="Parsifal Software"
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724 WIDTH=181 HEIGHT=25>
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725 <BR CLEAR="right">
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726
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727 <P>
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728 Back to :
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729 <A HREF="../../index.html">Index</A> |
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730 <A HREF="index.html">Macro preprocessor overview</A>
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731 <P>
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732
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733 <ADDRESS><FONT SIZE="-1">
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734 AnaGram parser generator - examples<BR>
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735 Token Scanner - Macro preprocessor and C Parser <BR>
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736 Copyright &copy; 1993-1999, Parsifal Software. <BR>
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737 All Rights Reserved.<BR>
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738 </FONT></ADDRESS>
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739
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740 </BODY>
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741 </HTML>
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742