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1 NAME
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2 Parsers::SimpleCalcParser
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3
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4 SYNOPSIS
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5 use Parsers::SimpleCalcParser ;
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6
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7 use Parsers::SimpleCalcParser qw(:all);
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8
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9 DESCRIPTION
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10 Parsers::SimpleCalcParser class provides the following methods:
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11
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12 new, yyclearin, yyerrok, yyerror, yyparse
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13
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14 Parsers::SimpleCalcParse.yy parser grammer definition file implements a
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15 simple calculator and is provided to highlight usage of lexer capability
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16 available through Parsers::SimpleCalcYYLexer, which in turn uses
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17 Parsers::YYLexer and Parsers::Lexer classes to procide underlying lexer
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18 functionality.
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19
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20 The parser package and token table files, Parsers::SimpleCalcParser.pm
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21 and SimpleCalcParser.tab.ph, are automatically generated from parser
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22 grammar definition file, Parsers::SimpleCalcParser.yy, using byacc
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23 available through perl-byacc1.8 modified with perl5-byacc-patches-0.5
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24 for generation of object oriented parser:
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25
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26 byacc -l -P -d -b SimpleCalcParser SimpleCalcParser.yy
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27 mv SimpleCalcParser.tab.pl SimpleCalcParser.pm
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28
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29 METHODS
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30 new
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31 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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32 \&Parsers::SimpleCalcParser::yyerror);
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33 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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34 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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35
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36 Using specified *YYLex* *YYError* functions, new method generates a
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37 new SimpleCalcParser and returns a reference to newly created
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38 SimpleCalcYYParser object.
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39
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40 Examples:
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41
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42 # Input string...
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43 $InputText = "3 + 4 +6\nx=3\ny=5\nx+y\nx+z\n";
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44 $YYLexer = new Parsers::SimpleCalcYYLexer($InputText);
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45 $YYLex = $YYLexer->GetYYLex();
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46
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47 $Debug = 0;
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48 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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49 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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50 $Value = $SimpleCalcParser->yyparse();
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51 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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52
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53 # Input file...
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54 $InputFile = "TestSimpleCalcParser.txt";
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55 open INPUTFILE, "$InputFile" or die "Couldn't open $InputFile: $!\n";
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56
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57 $YYLexer = new Parsers::SimpleCalcYYLexer(\*INPUTFILE);
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58 $YYLex = $YYLexer->GetYYLex();
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59
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60 $Debug = 0;
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61 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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62 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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63 $Value = $SimpleCalcParser->yyparse();
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64 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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65
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66 close INPUTFILE;
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67
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68 # Input iterator...
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69 $InputFile = "TestSimpleCalcParser.txt";
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70 open INPUTFILE, "$InputFile" or die "Couldn't open $InputFile: $!\n";
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71 $InputIterator = sub { return <INPUTFILE>; };
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72
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73 $YYLexer = new Parsers::SimpleCalcYYLexer($InputIterator);
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74 $YYLex = $YYLexer->GetYYLex();
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75
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76 $Debug = 0;
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77 $SimpleCalcParser = new Parsers::SimpleCalcParser($YYLex,
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78 \&Parsers::SimpleCalcParser::yyerror, $Debug);
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79 $Value = $SimpleCalcParser->yyparse();
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80 print "Value = " . (defined($Value) ? "$Value" : "Undefined") . "\n";
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81
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82 close INPUTFILE;
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83
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84 yyclearin
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85 $SimpleCalcParser->yyclearin();
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86
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87 yyclearin method clears any previous look-ahead token after
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88 encountering a syntax error during parsing. It can be used after
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89 yyerrok in a grammer rule with the reserved word error.
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90
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91 yyerrok
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92 $SimpleCalcParser->yyerrok();
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93
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94 yyerrok method is used with the reserved word error in grammer rule
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95 to indcate error recovery is complete after encountering a syntax
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96 error during parsing.
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97
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98 yyerror
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99 $SimpleCalcParser->yyerror();
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100
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101 yyerror function is provided for the caller to use during
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102 initialization of a parser. It is used by yyparse to print any error
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103 messages encountered during parsing of the input.
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104
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105 yyparse
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106 $Value = $SimpleCalcParser->yyparse();
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107
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108 Returns *Value* after parsing all the input from a input stream
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109 using specified grammer rules.
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110
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111 AUTHOR
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112 Manish Sud <msud@san.rr.com>
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113
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114 SEE ALSO
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115 Lexer.pm, YYLexer.pm, SimpleCalcYYLexer.pm
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116
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117 COPYRIGHT
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118 Copyright (C) 2015 Manish Sud. All rights reserved.
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119
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120 This file is part of MayaChemTools.
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121
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122 MayaChemTools is free software; you can redistribute it and/or modify it
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123 under the terms of the GNU Lesser General Public License as published by
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124 the Free Software Foundation; either version 3 of the License, or (at
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125 your option) any later version.
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126
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