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comparison mayachemtools/docs/modules/man3/Lexer.3 @ 0:73ae111cf86f draft
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date | Wed, 20 Jan 2016 11:55:01 -0500 |
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124 .\" ======================================================================== | |
125 .\" | |
126 .IX Title "LEXER 1" | |
127 .TH LEXER 1 "2015-03-29" "perl v5.14.2" "MayaChemTools" | |
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes | |
129 .\" way too many mistakes in technical documents. | |
130 .if n .ad l | |
131 .nh | |
132 .SH "NAME" | |
133 Parsers::Lexer | |
134 .SH "SYNOPSIS" | |
135 .IX Header "SYNOPSIS" | |
136 use Parsers::Lexer; | |
137 .PP | |
138 use Parsers::Lexer qw(:all); | |
139 .SH "DESCRIPTION" | |
140 .IX Header "DESCRIPTION" | |
141 \&\fBLexer\fR class provides the following methods: | |
142 .PP | |
143 new, GetLex, Lex, Next, Peek, StringifyLexer | |
144 .PP | |
145 The object oriented chained \fBLexer\fR is implemented based on examples available in | |
146 Higher-order Perl [ Ref 126 ] book by Mark J. Dominus. It is designed to be used | |
147 both in standalone mode or as a base class for \fBYYLexer\fR. | |
148 .PP | |
149 A chained lexer is created by generating a lexer for for the first specified token | |
150 specification using specified input and chaining it with other lexers generated for all | |
151 subsequent token specifications. The lexer generated for the first token specification | |
152 uses input iterator to retrieve any available input text; the subsequent chained lexeres | |
153 for rest of the token specifications use lexers generated for previous token | |
154 specifications to get next input, which might be unmatched input text or a reference | |
155 to an array containing token and matched text pair. | |
156 .SS "\s-1METHODS\s0" | |
157 .IX Subsection "METHODS" | |
158 .IP "\fBnew\fR" 4 | |
159 .IX Item "new" | |
160 .Vb 1 | |
161 \& $Lexer = new Parsers::Lexer($Input, @TokensSpec); | |
162 .Ve | |
163 .Sp | |
164 Using specified \fIInput\fR and \fITokensSpec\fR, \fBnew\fR method generates a new lexer | |
165 and returns a reference to newly created \fBLexer\fR object. | |
166 .Sp | |
167 Example: | |
168 .Sp | |
169 .Vb 10 | |
170 \& # Tokens specifications supplied by the caller. It\*(Aqs an array containing references | |
171 \& # to arrays with each containing TokenLabel and TokenMatchRegex pair along with | |
172 \& # an option reference to code to be executed after a matched. | |
173 \& # | |
174 \& @LexerTokensSpec = ( | |
175 \& [ \*(AqLETTER\*(Aq, qr/[a\-zA\-Z]/ ], | |
176 \& [ \*(AqNUMBER\*(Aq, qr/\ed+/ ], | |
177 \& [ \*(AqSPACE\*(Aq, qr/[ ]*/, | |
178 \& sub { my($This, $TokenLabel, $MatchedText) = @_; return \*(Aq\*(Aq; } | |
179 \& ], | |
180 \& [ \*(AqNEWLINE\*(Aq, qr/(?:\er\en|\er|\en)/, | |
181 \& sub { my($This, $TokenLabel, $MatchedText) = @_; return "\en"; } | |
182 \& ], | |
183 \& [ \*(AqCHAR\*(Aq, qr/./ ] | |
184 \& ); | |
185 \& | |
186 \& # Input string... | |
187 \& $InputText = \*(Aqy = 3 + 4\*(Aq; | |
188 \& $Lexer = new Parsers::Lexer($InputText, @LexerTokensSpec); | |
189 \& | |
190 \& # Process input stream... | |
191 \& while (defined($Token = $Lexer\->Lex())) { | |
192 \& print "Token: " . ((ref $Token) ? "@{$Token}" : "$Token") . "\en"; | |
193 \& } | |
194 \& | |
195 \& # Input file... | |
196 \& $InputFile = "Input.txt"; | |
197 \& open INPUTFILE, "$InputFile" or die "Couldn\*(Aqt open $InputFile: $!\en"; | |
198 \& $Lexer = new Parsers::Lexer(\e*INPUTFILE, @LexerTokensSpec); | |
199 \& | |
200 \& # Input file iterator... | |
201 \& $InputFile = "TestSimpleCalcParser.txt"; | |
202 \& open INPUTFILE, "$InputFile" or die "Couldn\*(Aqt open $InputFile: $!\en"; | |
203 \& $InputIterator = sub { return <INPUTFILE>; }; | |
204 \& $Lexer = new Parsers::Lexer($InputIterator, @LexerTokensSpec); | |
205 \& | |
206 \& @LexerTokensSpec = ( | |
207 \& [ \*(AqVAR\*(Aq, qr/[[:alpha:]]+/ ], | |
208 \& [ \*(AqNUM\*(Aq, qr/\ed+/ ], | |
209 \& [ \*(AqOP\*(Aq, qr/[\-+=\e/]/, | |
210 \& sub { my($This, $Label, $Value) = @_; | |
211 \& $Value .= "; ord: " . ord $Value; | |
212 \& return [$Label, $Value]; | |
213 \& } | |
214 \& ], | |
215 \& [ \*(AqNEWLINE\*(Aq, qr/(?:\er\en|\er|\en)/, sub { return [$_[1], \*(AqNewLine\*(Aq]; } ], | |
216 \& [ \*(AqSPACE\*(Aq, qr/\es*/, sub { return [$_[1], \*(AqSpace\*(Aq]; } ], | |
217 \& ); | |
218 \& | |
219 \& # Look ahead without removing... | |
220 \& $Token = $Lexer\->Lex(\*(AqPeek\*(Aq); | |
221 \& if (defined $Token && ref $Token) { | |
222 \& print "PEEK: Token: @{$Token}\en\en"; | |
223 \& } | |
224 \& | |
225 \& # Process input stream... | |
226 \& while (defined($Token = $Lexer\->Lex())) { | |
227 \& print "Token: " . ((ref $Token) ? "@{$Token}" : "$Token") . "\en"; | |
228 \& } | |
229 .Ve | |
230 .IP "\fBGetLex\fR" 4 | |
231 .IX Item "GetLex" | |
232 .Vb 1 | |
233 \& $LexerRef = $Lexer\->GetLex(); | |
234 .Ve | |
235 .Sp | |
236 Returns a refernece to \fILexer\fR method to the caller for use in a specific \fBYYLexer\fR. | |
237 .IP "\fBLex\fR" 4 | |
238 .IX Item "Lex" | |
239 .Vb 7 | |
240 \& $TokenRefOrText = $Lexer\->Lex($Mode); | |
241 \& if (ref $TokenRefOrText) { | |
242 \& ($TokenLabel, $TokenValue) = @{$TokenRefOrText}; | |
243 \& } | |
244 \& else { | |
245 \& $TokenText = $TokenRefOrText; | |
246 \& } | |
247 .Ve | |
248 .Sp | |
249 Get next available token label and value pair as an array reference or unrecognized | |
250 text from input stream by either removing it from the input or simply peeking ahead | |
251 and without removing it from the input stream. | |
252 .Sp | |
253 Possible \fIMode\fR values: \fIPeek, Next\fR. Default: \fINext\fR. | |
254 .IP "\fBNext\fR" 4 | |
255 .IX Item "Next" | |
256 .Vb 1 | |
257 \& $TokenRefOrText = $Lexer\->Next(); | |
258 .Ve | |
259 .Sp | |
260 Get next available token label and value pair as an array reference or unrecognized | |
261 text from input stream by removing it from the input stream. | |
262 .IP "\fBPeek\fR" 4 | |
263 .IX Item "Peek" | |
264 .Vb 1 | |
265 \& $TokenRefOrText = $Lexer\->Peek(); | |
266 .Ve | |
267 .Sp | |
268 Get next available token label and value pair as an array reference or unrecognized | |
269 text from input stream by by simply peeking ahead and without removing it from the | |
270 input stream. | |
271 .IP "\fBStringifyLexer\fR" 4 | |
272 .IX Item "StringifyLexer" | |
273 .Vb 1 | |
274 \& $LexerString = $Lexer\->StringifyLexer(); | |
275 .Ve | |
276 .Sp | |
277 Returns a string containing information about \fILexer\fR object. | |
278 .SH "AUTHOR" | |
279 .IX Header "AUTHOR" | |
280 Manish Sud <msud@san.rr.com> | |
281 .SH "SEE ALSO" | |
282 .IX Header "SEE ALSO" | |
283 YYLexer.pm, SimpleCalcYYLexer.pm, SimpleCalcParser.yy | |
284 .SH "COPYRIGHT" | |
285 .IX Header "COPYRIGHT" | |
286 Copyright (C) 2015 Manish Sud. All rights reserved. | |
287 .PP | |
288 This file is part of MayaChemTools. | |
289 .PP | |
290 MayaChemTools is free software; you can redistribute it and/or modify it under | |
291 the terms of the \s-1GNU\s0 Lesser General Public License as published by the Free | |
292 Software Foundation; either version 3 of the License, or (at your option) | |
293 any later version. |