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1 %{
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2 package Parsers::SimpleCalcParser;
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3 #
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4 # $RCSfile: SimpleCalcParser.yy,v $
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5 # $Date: 2015/02/28 20:50:55 $
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6 # $Revision: 1.10 $
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7 #
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8 # Author: Manish Sud <msud@san.rr.com>
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9 #
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10 # Copyright (C) 2015 Manish Sud. All rights reserved.
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11 #
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12 # This file is part of MayaChemTools.
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13 #
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14 # MayaChemTools is free software; you can redistribute it and/or modify it under
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15 # the terms of the GNU Lesser General Public License as published by the Free
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16 # Software Foundation; either version 3 of the License, or (at your option) any
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17 # later version.
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18 #
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19 # MayaChemTools is distributed in the hope that it will be useful, but without
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20 # any warranty; without even the implied warranty of merchantability of fitness
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21 # for a particular purpose. See the GNU Lesser General Public License for more
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22 # details.
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23 #
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24 # You should have received a copy of the GNU Lesser General Public License
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25 # along with MayaChemTools; if not, see <http://www.gnu.org/licenses/> or
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26 # write to the Free Software Foundation Inc., 59 Temple Place, Suite 330,
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27 # Boston, MA, 02111-1307, USA.
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28 #
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29 #
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30 # A WORD TO THE WISE:
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31 #
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32 # The parser package and token table files, SimpleCalcParser.pm and
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33 # SimpleCalcParser.tab.ph, are automatically generated from parser grammar
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34 # definition file, SimpleCalcParser.yy, using byacc available through perl-byacc1.8
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35 # modified with perl5-byacc-patches-0.5 for generation of object oriented parser:
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36 #
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37 # byacc -l -P -d -b SimpleCalcParser SimpleCalcParser.yy
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38 # mv SimpleCalcParser.tab.pl SimpleCalcParser.pm
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39 #
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40
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41 use Carp;
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42
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43 # Setup a hash map for mapping of words/letters to values...
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44 %LetterToValueMap = ();
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45
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46 %}
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47
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48 %start list
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49
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50 %token NUMBER LETTER
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51
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52 %left '+' '-'
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53 %left '*' '/'
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54 %left '%'
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55
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56 %%
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57
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58 list :
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59 | list stat '\n'
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60 { $$ = $2; }
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61 | list error '\n'
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62 { $p->yyerrok; $p->yyclearin; }
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63 ;
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64
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65
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66 stat : expr
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67 { $ExprOut = sprintf "%5i", $1; print "$ExprOut\n"; $$ = $1; }
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68 | LETTER '=' expr
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69 { $LetterToValueMap{$1} = $3; }
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70 ;
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71
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72 expr : '(' expr ')'
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73 { $$ = $2; }
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74 | expr '+' expr
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75 { $$ = $1 + $3; }
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76 | expr '-' expr
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77 { $$ = $1 - $3; }
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78 | expr '*' expr
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79 { $$ = $1 * $3; }
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80 | expr '/' expr
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81 { $$ = $1 / $3; }
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82 | expr '%' expr
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83 { $$ = $1 % $3; }
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84 | NUMBER
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85 | LETTER
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86 {
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87 if (exists $LetterToValueMap{$1}) {
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88 $$ = $LetterToValueMap{$1};
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89 }
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90 else {
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91 $Letter = $1;
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92 print "Undefined variable $Letter encountered by SimpleCalcParser; Value set to 0\n";
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93 $$ = 0;
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94 }
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95 }
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96 ;
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97
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98 %%
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99
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100 # yyerror function supplied to parser along with a lexer during initialization of
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101 # the parser...
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102 #
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103 sub yyerror {
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104 my ($msg) = @_;
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105 print "yyerror: $msg...\n";
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106 }
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107
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108 1;
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109
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110 __END__
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111
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112 =head1 NAME
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113
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114 Parsers::SimpleCalcParser
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115
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116 =head1 SYNOPSIS
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117
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118 use Parsers::SimpleCalcParser ;
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119
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120 use Parsers::SimpleCalcParser qw(:all);
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121
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122 =head1 DESCRIPTION
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123
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124 B<Parsers::SimpleCalcParser> class provides the following methods:
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125
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126 new, yyclearin, yyerrok, yyerror, yyparse
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127
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128 B<Parsers::SimpleCalcParse.yy> parser grammer definition file implements a simple
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129 calculator and is provided to highlight usage of lexer capability available through
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130 B<Parsers::SimpleCalcYYLexer>, which in turn uses B<Parsers::YYLexer> and
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131 B<Parsers::Lexer> classes to procide underlying lexer functionality.
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132
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133 The parser package and token table files, B<Parsers::SimpleCalcParser.pm> and
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134 B<SimpleCalcParser.tab.ph>, are automatically generated from parser grammar definition
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135 file, B<Parsers::SimpleCalcParser.yy>, using byacc available through perl-byacc1.8 modified
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136 with perl5-byacc-patches-0.5 for generation of object oriented parser:
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137
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138 byacc -l -P -d -b SimpleCalcParser SimpleCalcParser.yy
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139 mv SimpleCalcParser.tab.pl SimpleCalcParser.pm
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140
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141 =head2 METHODS
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142
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143 =over 4
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144
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145 =item B<new>
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146
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147 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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148 \&Parsers::SimpleCalcParser::yyerror);
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149 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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150 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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151
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152 Using specified I<YYLex> I<YYError> functions, B<new> method generates a new
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153 B<SimpleCalcParser> and returns a reference to newly created B<SimpleCalcYYParser> object.
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154
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155 Examples:
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156
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157 # Input string...
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158 $InputText = "3 + 4 +6\nx=3\ny=5\nx+y\nx+z\n";
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159 $YYLexer = new Parsers::SimpleCalcYYLexer($InputText);
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160 $YYLex = $YYLexer->GetYYLex();
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161
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162 $Debug = 0;
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163 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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164 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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165 $Value = $SimpleCalcParser->yyparse();
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166 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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167
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168 # Input file...
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169 $InputFile = "TestSimpleCalcParser.txt";
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170 open INPUTFILE, "$InputFile" or die "Couldn't open $InputFile: $!\n";
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171
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172 $YYLexer = new Parsers::SimpleCalcYYLexer(\*INPUTFILE);
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173 $YYLex = $YYLexer->GetYYLex();
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174
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175 $Debug = 0;
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176 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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177 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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178 $Value = $SimpleCalcParser->yyparse();
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179 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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180
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181 close INPUTFILE;
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182
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183 # Input iterator...
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184 $InputFile = "TestSimpleCalcParser.txt";
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185 open INPUTFILE, "$InputFile" or die "Couldn't open $InputFile: $!\n";
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186 $InputIterator = sub { return <INPUTFILE>; };
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187
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188 $YYLexer = new Parsers::SimpleCalcYYLexer($InputIterator);
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189 $YYLex = $YYLexer->GetYYLex();
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190
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191 $Debug = 0;
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192 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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193 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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194 $Value = $SimpleCalcParser->yyparse();
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195 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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196
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197 close INPUTFILE;
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198
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199 =item B<yyclearin>
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200
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201 $SimpleCalcParser->yyclearin();
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202
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203 B<yyclearin> method clears any previous look-ahead token after encountering a syntax error
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204 during parsing. It can be used after B<yyerrok> in a grammer rule with the reserved word
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205 B<error>.
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206
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207 =item B<yyerrok>
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208
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209 $SimpleCalcParser->yyerrok();
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210
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211 B<yyerrok> method is used with the reserved word B<error> in grammer rule to indcate
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212 error recovery is complete after encountering a syntax error during parsing.
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213
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214 =item B<yyerror>
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215
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216 $SimpleCalcParser->yyerror();
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217
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218 B<yyerror> function is provided for the caller to use during initialization of a parser. It
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219 is used by B<yyparse> to print any error messages encountered during parsing of the
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220 input.
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221
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222 =item B<yyparse>
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223
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224 $Value = $SimpleCalcParser->yyparse();
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225
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226 Returns I<Value> after parsing all the input from a input stream using specified
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227 grammer rules.
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228
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229 =back
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230
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231 =head1 AUTHOR
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232
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233 Manish Sud <msud@san.rr.com>
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234
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235 =head1 SEE ALSO
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236
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237 Lexer.pm, YYLexer.pm, SimpleCalcYYLexer.pm
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238
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239 =head1 COPYRIGHT
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240
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241 Copyright (C) 2015 Manish Sud. All rights reserved.
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242
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243 This file is part of MayaChemTools.
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244
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245 MayaChemTools is free software; you can redistribute it and/or modify it under
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246 the terms of the GNU Lesser General Public License as published by the Free
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247 Software Foundation; either version 3 of the License, or (at your option)
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248 any later version.
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249
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250 =cut
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251
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