| 3eb9473e |
1 | ======================================================================\r |
| 2 | \r |
| 3 | CHANGES_SUMMARY.TXT\r |
| 4 | \r |
| 5 | A QUICK overview of changes from 1.33 in reverse order\r |
| 6 | \r |
| 7 | A summary of additions rather than bug fixes and minor code changes.\r |
| 8 | \r |
| 9 | Numbers refer to items in CHANGES_FROM_133*.TXT\r |
| 10 | which may contain additional information.\r |
| 11 | \r |
| 12 | DISCLAIMER\r |
| 13 | \r |
| 14 | The software and these notes are provided "as is". They may include\r |
| 15 | typographical or technical errors and their authors disclaims all\r |
| 16 | liability of any kind or nature for damages due to error, fault,\r |
| 17 | defect, or deficiency regardless of cause. All warranties of any\r |
| 18 | kind, either express or implied, including, but not limited to, the\r |
| 19 | implied warranties of merchantability and fitness for a particular\r |
| 20 | purpose are disclaimed.\r |
| 21 | \r |
| 22 | ======================================================================\r |
| 23 | \r |
| 24 | #258. You can specify a user-defined base class for your parser\r |
| 25 | \r |
| 26 | The base class must constructor must have a signature similar to\r |
| 27 | that of ANTLRParser.\r |
| 28 | \r |
| 29 | #253. Generation of block preamble (-preamble and -preamble_first)\r |
| 30 | \r |
| 31 | The antlr option -preamble causes antlr to insert the code\r |
| 32 | BLOCK_PREAMBLE at the start of each rule and block.\r |
| 33 | \r |
| 34 | The antlr option -preamble_first is similar, but inserts the\r |
| 35 | code BLOCK_PREAMBLE_FIRST(PreambleFirst_123) where the symbol\r |
| 36 | PreambleFirst_123 is equivalent to the first set defined by\r |
| 37 | the #FirstSetSymbol described in Item #248.\r |
| 38 | \r |
| 39 | #248. Generate symbol for first set of an alternative\r |
| 40 | \r |
| 41 | rr : #FirstSetSymbol(rr_FirstSet) ( Foo | Bar ) ;\r |
| 42 | \r |
| 43 | #216. Defer token fetch for C++ mode\r |
| 44 | \r |
| 45 | When the ANTLRParser class is built with the pre-processor option \r |
| 46 | ZZDEFER_FETCH defined, the fetch of new tokens by consume() is deferred\r |
| 47 | until LA(i) or LT(i) is called. \r |
| 48 | \r |
| 49 | #215. Use reset() to reset DLGLexerBase\r |
| 50 | #188. Added pccts/h/DLG_stream_input.h\r |
| 51 | #180. Added ANTLRParser::getEofToken()\r |
| 52 | #173. -glms for Microsoft style filenames with -gl\r |
| 53 | #170. Suppression for predicates with lookahead depth >1\r |
| 54 | \r |
| 55 | Consider the following grammar with -ck 2 and the predicate in rule\r |
| 56 | "a" with depth 2:\r |
| 57 | \r |
| 58 | r1 : (ab)* "@"\r |
| 59 | ;\r |
| 60 | \r |
| 61 | ab : a\r |
| 62 | | b\r |
| 63 | ;\r |
| 64 | \r |
| 65 | a : (A B)? => <<p(LATEXT(2))>>? A B C\r |
| 66 | ;\r |
| 67 | \r |
| 68 | b : A B C\r |
| 69 | ;\r |
| 70 | \r |
| 71 | Normally, the predicate would be hoisted into rule r1 in order to\r |
| 72 | determine whether to call rule "ab". However it should *not* be\r |
| 73 | hoisted because, even if p is false, there is a valid alternative\r |
| 74 | in rule b. With "-mrhoistk on" the predicate will be suppressed.\r |
| 75 | \r |
| 76 | If "-info p" command line option is present the following information\r |
| 77 | will appear in the generated code:\r |
| 78 | \r |
| 79 | while ( (LA(1)==A)\r |
| 80 | #if 0\r |
| 81 | \r |
| 82 | Part (or all) of predicate with depth > 1 suppressed by alternative\r |
| 83 | without predicate\r |
| 84 | \r |
| 85 | pred << p(LATEXT(2))>>?\r |
| 86 | depth=k=2 ("=>" guard) rule a line 8 t1.g\r |
| 87 | tree context:\r |
| 88 | (root = A\r |
| 89 | B\r |
| 90 | )\r |
| 91 | \r |
| 92 | The token sequence which is suppressed: ( A B )\r |
| 93 | The sequence of references which generate that sequence of tokens:\r |
| 94 | \r |
| 95 | 1 to ab r1/1 line 1 t1.g\r |
| 96 | 2 ab ab/1 line 4 t1.g\r |
| 97 | 3 to b ab/2 line 5 t1.g\r |
| 98 | 4 b b/1 line 11 t1.g\r |
| 99 | 5 #token A b/1 line 11 t1.g\r |
| 100 | 6 #token B b/1 line 11 t1.g\r |
| 101 | \r |
| 102 | #endif\r |
| 103 | \r |
| 104 | A slightly more complicated example:\r |
| 105 | \r |
| 106 | r1 : (ab)* "@"\r |
| 107 | ;\r |
| 108 | \r |
| 109 | ab : a\r |
| 110 | | b\r |
| 111 | ;\r |
| 112 | \r |
| 113 | a : (A B)? => <<p(LATEXT(2))>>? (A B | D E)\r |
| 114 | ;\r |
| 115 | \r |
| 116 | b : <<q(LATEXT(2))>>? D E\r |
| 117 | ;\r |
| 118 | \r |
| 119 | \r |
| 120 | In this case, the sequence (D E) in rule "a" which lies behind\r |
| 121 | the guard is used to suppress the predicate with context (D E)\r |
| 122 | in rule b.\r |
| 123 | \r |
| 124 | while ( (LA(1)==A || LA(1)==D)\r |
| 125 | #if 0\r |
| 126 | \r |
| 127 | Part (or all) of predicate with depth > 1 suppressed by alternative\r |
| 128 | without predicate\r |
| 129 | \r |
| 130 | pred << q(LATEXT(2))>>?\r |
| 131 | depth=k=2 rule b line 11 t2.g\r |
| 132 | tree context:\r |
| 133 | (root = D\r |
| 134 | E\r |
| 135 | )\r |
| 136 | \r |
| 137 | The token sequence which is suppressed: ( D E )\r |
| 138 | The sequence of references which generate that sequence of tokens:\r |
| 139 | \r |
| 140 | 1 to ab r1/1 line 1 t2.g\r |
| 141 | 2 ab ab/1 line 4 t2.g\r |
| 142 | 3 to a ab/1 line 4 t2.g\r |
| 143 | 4 a a/1 line 8 t2.g\r |
| 144 | 5 #token D a/1 line 8 t2.g\r |
| 145 | 6 #token E a/1 line 8 t2.g\r |
| 146 | \r |
| 147 | #endif\r |
| 148 | &&\r |
| 149 | #if 0\r |
| 150 | \r |
| 151 | pred << p(LATEXT(2))>>?\r |
| 152 | depth=k=2 ("=>" guard) rule a line 8 t2.g\r |
| 153 | tree context:\r |
| 154 | (root = A\r |
| 155 | B\r |
| 156 | )\r |
| 157 | \r |
| 158 | #endif\r |
| 159 | \r |
| 160 | (! ( LA(1)==A && LA(2)==B ) || p(LATEXT(2)) ) {\r |
| 161 | ab();\r |
| 162 | ...\r |
| 163 | \r |
| 164 | #165. (Changed in MR13) option -newAST\r |
| 165 | \r |
| 166 | To create ASTs from an ANTLRTokenPtr antlr usually calls\r |
| 167 | "new AST(ANTLRTokenPtr)". This option generates a call\r |
| 168 | to "newAST(ANTLRTokenPtr)" instead. This allows a user\r |
| 169 | to define a parser member function to create an AST object.\r |
| 170 | \r |
| 171 | #161. (Changed in MR13) Switch -gxt inhibits generation of tokens.h\r |
| 172 | \r |
| 173 | #158. (Changed in MR13) #header causes problem for pre-processors\r |
| 174 | \r |
| 175 | A user who runs the C pre-processor on antlr source suggested\r |
| 176 | that another syntax be allowed. With MR13 such directives\r |
| 177 | such as #header, #pragma, etc. may be written as "\#header",\r |
| 178 | "\#pragma", etc. For escaping pre-processor directives inside\r |
| 179 | a #header use something like the following:\r |
| 180 | \r |
| 181 | \#header\r |
| 182 | <<\r |
| 183 | \#include <stdio.h>\r |
| 184 | >>\r |
| 185 | \r |
| 186 | #155. (Changed in MR13) Context behind predicates can suppress\r |
| 187 | \r |
| 188 | With -mrhoist enabled the context behind a guarded predicate can\r |
| 189 | be used to suppress other predicates. Consider the following grammar:\r |
| 190 | \r |
| 191 | r0 : (r1)+;\r |
| 192 | \r |
| 193 | r1 : rp\r |
| 194 | | rq\r |
| 195 | ;\r |
| 196 | rp : <<p LATEXT(1)>>? B ;\r |
| 197 | rq : (A)? => <<q LATEXT(1)>>? (A|B);\r |
| 198 | \r |
| 199 | In earlier versions both predicates "p" and "q" would be hoisted into\r |
| 200 | rule r0. With MR12c predicate p is suppressed because the context which\r |
| 201 | follows predicate q includes "B" which can "cover" predicate "p". In\r |
| 202 | other words, in trying to decide in r0 whether to call r1, it doesn't\r |
| 203 | really matter whether p is false or true because, either way, there is\r |
| 204 | a valid choice within r1.\r |
| 205 | \r |
| 206 | #154. (Changed in MR13) Making hoist suppression explicit using <<nohoist>>\r |
| 207 | \r |
| 208 | A common error, even among experienced pccts users, is to code\r |
| 209 | an init-action to inhibit hoisting rather than a leading action.\r |
| 210 | An init-action does not inhibit hoisting.\r |
| 211 | \r |
| 212 | This was coded:\r |
| 213 | \r |
| 214 | rule1 : <<;>> rule2\r |
| 215 | \r |
| 216 | This is what was meant:\r |
| 217 | \r |
| 218 | rule1 : <<;>> <<;>> rule2\r |
| 219 | \r |
| 220 | With MR13, the user can code:\r |
| 221 | \r |
| 222 | rule1 : <<;>> <<nohoist>> rule2\r |
| 223 | \r |
| 224 | The following will give an error message:\r |
| 225 | \r |
| 226 | rule1 : <<nohoist>> rule2\r |
| 227 | \r |
| 228 | If the <<nohoist>> appears as an init-action rather than a leading\r |
| 229 | action an error message is issued. The meaning of an init-action\r |
| 230 | containing "nohoist" is unclear: does it apply to just one\r |
| 231 | alternative or to all alternatives ?\r |
| 232 | \r |
| 233 | #151a. Addition of ANTLRParser::getLexer(), ANTLRTokenStream::getLexer()\r |
| 234 | \r |
| 235 | You must manually cast the ANTLRTokenStream to your program's\r |
| 236 | lexer class. Because the name of the lexer's class is not fixed.\r |
| 237 | Thus it is impossible to incorporate it into the DLGLexerBase\r |
| 238 | class.\r |
| 239 | \r |
| 240 | #151b.(Changed in MR12) ParserBlackBox member getLexer()\r |
| 241 | \r |
| 242 | #150. (Changed in MR12) syntaxErrCount and lexErrCount now public\r |
| 243 | \r |
| 244 | #149. (Changed in MR12) antlr option -info o (letter o for orphan)\r |
| 245 | \r |
| 246 | If there is more than one rule which is not referenced by any\r |
| 247 | other rule then all such rules are listed. This is useful for\r |
| 248 | alerting one to rules which are not used, but which can still\r |
| 249 | contribute to ambiguity.\r |
| 250 | \r |
| 251 | #148. (Changed in MR11) #token names appearing in zztokens,token_tbl\r |
| 252 | \r |
| 253 | One can write:\r |
| 254 | \r |
| 255 | #token Plus ("+") "\+"\r |
| 256 | #token RP ("(") "\("\r |
| 257 | #token COM ("comment begin") "/\*"\r |
| 258 | \r |
| 259 | The string in parenthesis will be used in syntax error messages.\r |
| 260 | \r |
| 261 | #146. (Changed in MR11) Option -treport for locating "difficult" alts\r |
| 262 | \r |
| 263 | It can be difficult to determine which alternatives are causing\r |
| 264 | pccts to work hard to resolve an ambiguity. In some cases the\r |
| 265 | ambiguity is successfully resolved after much CPU time so there\r |
| 266 | is no message at all.\r |
| 267 | \r |
| 268 | A rough measure of the amount of work being peformed which is\r |
| 269 | independent of the CPU speed and system load is the number of\r |
| 270 | tnodes created. Using "-info t" gives information about the\r |
| 271 | total number of tnodes created and the peak number of tnodes.\r |
| 272 | \r |
| 273 | Tree Nodes: peak 1300k created 1416k lost 0\r |
| 274 | \r |
| 275 | It also puts in the generated C or C++ file the number of tnodes\r |
| 276 | created for a rule (at the end of the rule). However this\r |
| 277 | information is not sufficient to locate the alternatives within\r |
| 278 | a rule which are causing the creation of tnodes.\r |
| 279 | \r |
| 280 | Using:\r |
| 281 | \r |
| 282 | antlr -treport 100000 ....\r |
| 283 | \r |
| 284 | causes antlr to list on stdout any alternatives which require the\r |
| 285 | creation of more than 100,000 tnodes, along with the lookahead sets\r |
| 286 | for those alternatives.\r |
| 287 | \r |
| 288 | The following is a trivial case from the ansi.g grammar which shows\r |
| 289 | the format of the report. This report might be of more interest\r |
| 290 | in cases where 1,000,000 tuples were created to resolve the ambiguity.\r |
| 291 | \r |
| 292 | -------------------------------------------------------------------------\r |
| 293 | There were 0 tuples whose ambiguity could not be resolved\r |
| 294 | by full lookahead\r |
| 295 | There were 157 tnodes created to resolve ambiguity between:\r |
| 296 | \r |
| 297 | Choice 1: statement/2 line 475 file ansi.g\r |
| 298 | Choice 2: statement/3 line 476 file ansi.g\r |
| 299 | \r |
| 300 | Intersection of lookahead[1] sets:\r |
| 301 | \r |
| 302 | IDENTIFIER\r |
| 303 | \r |
| 304 | Intersection of lookahead[2] sets:\r |
| 305 | \r |
| 306 | LPARENTHESIS COLON AMPERSAND MINUS\r |
| 307 | STAR PLUSPLUS MINUSMINUS ONESCOMPLEMENT\r |
| 308 | NOT SIZEOF OCTALINT DECIMALINT\r |
| 309 | HEXADECIMALINT FLOATONE FLOATTWO IDENTIFIER\r |
| 310 | STRING CHARACTER\r |
| 311 | -------------------------------------------------------------------------\r |
| 312 | \r |
| 313 | #143. (Changed in MR11) Optional ";" at end of #token statement\r |
| 314 | \r |
| 315 | Fixes problem of:\r |
| 316 | \r |
| 317 | #token X "x"\r |
| 318 | \r |
| 319 | <<\r |
| 320 | parser action\r |
| 321 | >>\r |
| 322 | \r |
| 323 | Being confused with:\r |
| 324 | \r |
| 325 | #token X "x" <<lexical action>>\r |
| 326 | \r |
| 327 | #142. (Changed in MR11) class BufFileInput subclass of DLGInputStream\r |
| 328 | \r |
| 329 | Alexey Demakov (demakov@kazbek.ispras.ru) has supplied class\r |
| 330 | BufFileInput derived from DLGInputStream which provides a\r |
| 331 | function lookahead(char *string) to test characters in the\r |
| 332 | input stream more than one character ahead.\r |
| 333 | The class is located in pccts/h/BufFileInput.* of the kit.\r |
| 334 | \r |
| 335 | #140. #pred to define predicates\r |
| 336 | \r |
| 337 | +---------------------------------------------------+\r |
| 338 | | Note: Assume "-prc on" for this entire discussion |\r |
| 339 | +---------------------------------------------------+\r |
| 340 | \r |
| 341 | A problem with predicates is that each one is regarded as\r |
| 342 | unique and capable of disambiguating cases where two\r |
| 343 | alternatives have identical lookahead. For example:\r |
| 344 | \r |
| 345 | rule : <<pred(LATEXT(1))>>? A\r |
| 346 | | <<pred(LATEXT(1))>>? A\r |
| 347 | ;\r |
| 348 | \r |
| 349 | will not cause any error messages or warnings to be issued\r |
| 350 | by earlier versions of pccts. To compare the text of the\r |
| 351 | predicates is an incomplete solution.\r |
| 352 | \r |
| 353 | In 1.33MR11 I am introducing the #pred statement in order to\r |
| 354 | solve some problems with predicates. The #pred statement allows\r |
| 355 | one to give a symbolic name to a "predicate literal" or a\r |
| 356 | "predicate expression" in order to refer to it in other predicate\r |
| 357 | expressions or in the rules of the grammar.\r |
| 358 | \r |
| 359 | The predicate literal associated with a predicate symbol is C\r |
| 360 | or C++ code which can be used to test the condition. A\r |
| 361 | predicate expression defines a predicate symbol in terms of other\r |
| 362 | predicate symbols using "!", "&&", and "||". A predicate symbol\r |
| 363 | can be defined in terms of a predicate literal, a predicate\r |
| 364 | expression, or *both*.\r |
| 365 | \r |
| 366 | When a predicate symbol is defined with both a predicate literal\r |
| 367 | and a predicate expression, the predicate literal is used to generate\r |
| 368 | code, but the predicate expression is used to check for two\r |
| 369 | alternatives with identical predicates in both alternatives.\r |
| 370 | \r |
| 371 | Here are some examples of #pred statements:\r |
| 372 | \r |
| 373 | #pred IsLabel <<isLabel(LATEXT(1))>>?\r |
| 374 | #pred IsLocalVar <<isLocalVar(LATEXT(1))>>?\r |
| 375 | #pred IsGlobalVar <<isGlobalVar(LATEXT(1)>>?\r |
| 376 | #pred IsVar <<isVar(LATEXT(1))>>? IsLocalVar || IsGlobalVar\r |
| 377 | #pred IsScoped <<isScoped(LATEXT(1))>>? IsLabel || IsLocalVar\r |
| 378 | \r |
| 379 | I hope that the use of EBNF notation to describe the syntax of the\r |
| 380 | #pred statement will not cause problems for my readers (joke).\r |
| 381 | \r |
| 382 | predStatement : "#pred"\r |
| 383 | CapitalizedName\r |
| 384 | (\r |
| 385 | "<<predicate_literal>>?"\r |
| 386 | | "<<predicate_literal>>?" predOrExpr\r |
| 387 | | predOrExpr\r |
| 388 | )\r |
| 389 | ;\r |
| 390 | \r |
| 391 | predOrExpr : predAndExpr ( "||" predAndExpr ) * ;\r |
| 392 | \r |
| 393 | predAndExpr : predPrimary ( "&&" predPrimary ) * ;\r |
| 394 | \r |
| 395 | predPrimary : CapitalizedName\r |
| 396 | | "!" predPrimary\r |
| 397 | | "(" predOrExpr ")"\r |
| 398 | ;\r |
| 399 | \r |
| 400 | What is the purpose of this nonsense ?\r |
| 401 | \r |
| 402 | To understand how predicate symbols help, you need to realize that\r |
| 403 | predicate symbols are used in two different ways with two different\r |
| 404 | goals.\r |
| 405 | \r |
| 406 | a. Allow simplification of predicates which have been combined\r |
| 407 | during predicate hoisting.\r |
| 408 | \r |
| 409 | b. Allow recognition of identical predicates which can't disambiguate\r |
| 410 | alternatives with common lookahead.\r |
| 411 | \r |
| 412 | First we will discuss goal (a). Consider the following rule:\r |
| 413 | \r |
| 414 | rule0: rule1\r |
| 415 | | ID\r |
| 416 | | ...\r |
| 417 | ;\r |
| 418 | \r |
| 419 | rule1: rule2\r |
| 420 | | rule3\r |
| 421 | ;\r |
| 422 | \r |
| 423 | rule2: <<isX(LATEXT(1))>>? ID ;\r |
| 424 | rule3: <<!isX(LATEXT(1)>>? ID ;\r |
| 425 | \r |
| 426 | When the predicates in rule2 and rule3 are combined by hoisting\r |
| 427 | to create a prediction expression for rule1 the result is:\r |
| 428 | \r |
| 429 | if ( LA(1)==ID\r |
| 430 | && ( isX(LATEXT(1) || !isX(LATEXT(1) ) ) { rule1(); ...\r |
| 431 | \r |
| 432 | This is inefficient, but more importantly, can lead to false\r |
| 433 | assumptions that the predicate expression distinguishes the rule1\r |
| 434 | alternative with some other alternative with lookahead ID. In\r |
| 435 | MR11 one can write:\r |
| 436 | \r |
| 437 | #pred IsX <<isX(LATEXT(1))>>?\r |
| 438 | \r |
| 439 | ...\r |
| 440 | \r |
| 441 | rule2: <<IsX>>? ID ;\r |
| 442 | rule3: <<!IsX>>? ID ;\r |
| 443 | \r |
| 444 | During hoisting MR11 recognizes this as a special case and\r |
| 445 | eliminates the predicates. The result is a prediction\r |
| 446 | expression like the following:\r |
| 447 | \r |
| 448 | if ( LA(1)==ID ) { rule1(); ...\r |
| 449 | \r |
| 450 | Please note that the following cases which appear to be equivalent\r |
| 451 | *cannot* be simplified by MR11 during hoisting because the hoisting\r |
| 452 | logic only checks for a "!" in the predicate action, not in the\r |
| 453 | predicate expression for a predicate symbol.\r |
| 454 | \r |
| 455 | *Not* equivalent and is not simplified during hoisting:\r |
| 456 | \r |
| 457 | #pred IsX <<isX(LATEXT(1))>>?\r |
| 458 | #pred NotX <<!isX(LATEXT(1))>>?\r |
| 459 | ...\r |
| 460 | rule2: <<IsX>>? ID ;\r |
| 461 | rule3: <<NotX>>? ID ;\r |
| 462 | \r |
| 463 | *Not* equivalent and is not simplified during hoisting:\r |
| 464 | \r |
| 465 | #pred IsX <<isX(LATEXT(1))>>?\r |
| 466 | #pred NotX !IsX\r |
| 467 | ...\r |
| 468 | rule2: <<IsX>>? ID ;\r |
| 469 | rule3: <<NotX>>? ID ;\r |
| 470 | \r |
| 471 | Now we will discuss goal (b).\r |
| 472 | \r |
| 473 | When antlr discovers that there is a lookahead ambiguity between\r |
| 474 | two alternatives it attempts to resolve the ambiguity by searching\r |
| 475 | for predicates in both alternatives. In the past any predicate\r |
| 476 | would do, even if the same one appeared in both alternatives:\r |
| 477 | \r |
| 478 | rule: <<p(LATEXT(1))>>? X\r |
| 479 | | <<p(LATEXT(1))>>? X\r |
| 480 | ;\r |
| 481 | \r |
| 482 | The #pred statement is a start towards solving this problem.\r |
| 483 | During ambiguity resolution (*not* predicate hoisting) the\r |
| 484 | predicates for the two alternatives are expanded and compared.\r |
| 485 | Consider the following example:\r |
| 486 | \r |
| 487 | #pred Upper <<isUpper(LATEXT(1))>>?\r |
| 488 | #pred Lower <<isLower(LATEXT(1))>>?\r |
| 489 | #pred Alpha <<isAlpha(LATEXT(1))>>? Upper || Lower\r |
| 490 | \r |
| 491 | rule0: rule1\r |
| 492 | | <<Alpha>>? ID\r |
| 493 | ;\r |
| 494 | \r |
| 495 | rule1:\r |
| 496 | | rule2\r |
| 497 | | rule3\r |
| 498 | ...\r |
| 499 | ;\r |
| 500 | \r |
| 501 | rule2: <<Upper>>? ID;\r |
| 502 | rule3: <<Lower>>? ID;\r |
| 503 | \r |
| 504 | The definition of #pred Alpha expresses:\r |
| 505 | \r |
| 506 | a. to test the predicate use the C code "isAlpha(LATEXT(1))"\r |
| 507 | \r |
| 508 | b. to analyze the predicate use the information that\r |
| 509 | Alpha is equivalent to the union of Upper and Lower,\r |
| 510 | \r |
| 511 | During ambiguity resolution the definition of Alpha is expanded\r |
| 512 | into "Upper || Lower" and compared with the predicate in the other\r |
| 513 | alternative, which is also "Upper || Lower". Because they are\r |
| 514 | identical MR11 will report a problem.\r |
| 515 | \r |
| 516 | -------------------------------------------------------------------------\r |
| 517 | t10.g, line 5: warning: the predicates used to disambiguate rule rule0\r |
| 518 | (file t10.g alt 1 line 5 and alt 2 line 6)\r |
| 519 | are identical when compared without context and may have no\r |
| 520 | resolving power for some lookahead sequences.\r |
| 521 | -------------------------------------------------------------------------\r |
| 522 | \r |
| 523 | If you use the "-info p" option the output file will contain:\r |
| 524 | \r |
| 525 | +----------------------------------------------------------------------+\r |
| 526 | |#if 0 |\r |
| 527 | | |\r |
| 528 | |The following predicates are identical when compared without |\r |
| 529 | | lookahead context information. For some ambiguous lookahead |\r |
| 530 | | sequences they may not have any power to resolve the ambiguity. |\r |
| 531 | | |\r |
| 532 | |Choice 1: rule0/1 alt 1 line 5 file t10.g |\r |
| 533 | | |\r |
| 534 | | The original predicate for choice 1 with available context |\r |
| 535 | | information: |\r |
| 536 | | |\r |
| 537 | | OR expr |\r |
| 538 | | |\r |
| 539 | | pred << Upper>>? |\r |
| 540 | | depth=k=1 rule rule2 line 14 t10.g |\r |
| 541 | | set context: |\r |
| 542 | | ID |\r |
| 543 | | |\r |
| 544 | | pred << Lower>>? |\r |
| 545 | | depth=k=1 rule rule3 line 15 t10.g |\r |
| 546 | | set context: |\r |
| 547 | | ID |\r |
| 548 | | |\r |
| 549 | | The predicate for choice 1 after expansion (but without context |\r |
| 550 | | information): |\r |
| 551 | | |\r |
| 552 | | OR expr |\r |
| 553 | | |\r |
| 554 | | pred << isUpper(LATEXT(1))>>? |\r |
| 555 | | depth=k=1 rule line 1 t10.g |\r |
| 556 | | |\r |
| 557 | | pred << isLower(LATEXT(1))>>? |\r |
| 558 | | depth=k=1 rule line 2 t10.g |\r |
| 559 | | |\r |
| 560 | | |\r |
| 561 | |Choice 2: rule0/2 alt 2 line 6 file t10.g |\r |
| 562 | | |\r |
| 563 | | The original predicate for choice 2 with available context |\r |
| 564 | | information: |\r |
| 565 | | |\r |
| 566 | | pred << Alpha>>? |\r |
| 567 | | depth=k=1 rule rule0 line 6 t10.g |\r |
| 568 | | set context: |\r |
| 569 | | ID |\r |
| 570 | | |\r |
| 571 | | The predicate for choice 2 after expansion (but without context |\r |
| 572 | | information): |\r |
| 573 | | |\r |
| 574 | | OR expr |\r |
| 575 | | |\r |
| 576 | | pred << isUpper(LATEXT(1))>>? |\r |
| 577 | | depth=k=1 rule line 1 t10.g |\r |
| 578 | | |\r |
| 579 | | pred << isLower(LATEXT(1))>>? |\r |
| 580 | | depth=k=1 rule line 2 t10.g |\r |
| 581 | | |\r |
| 582 | | |\r |
| 583 | |#endif |\r |
| 584 | +----------------------------------------------------------------------+\r |
| 585 | \r |
| 586 | The comparison of the predicates for the two alternatives takes\r |
| 587 | place without context information, which means that in some cases\r |
| 588 | the predicates will be considered identical even though they operate\r |
| 589 | on disjoint lookahead sets. Consider:\r |
| 590 | \r |
| 591 | #pred Alpha\r |
| 592 | \r |
| 593 | rule1: <<Alpha>>? ID\r |
| 594 | | <<Alpha>>? Label\r |
| 595 | ;\r |
| 596 | \r |
| 597 | Because the comparison of predicates takes place without context\r |
| 598 | these will be considered identical. The reason for comparing\r |
| 599 | without context is that otherwise it would be necessary to re-evaluate\r |
| 600 | the entire predicate expression for each possible lookahead sequence.\r |
| 601 | This would require more code to be written and more CPU time during\r |
| 602 | grammar analysis, and it is not yet clear whether anyone will even make\r |
| 603 | use of the new #pred facility.\r |
| 604 | \r |
| 605 | A temporary workaround might be to use different #pred statements\r |
| 606 | for predicates you know have different context. This would avoid\r |
| 607 | extraneous warnings.\r |
| 608 | \r |
| 609 | The above example might be termed a "false positive". Comparison\r |
| 610 | without context will also lead to "false negatives". Consider the\r |
| 611 | following example:\r |
| 612 | \r |
| 613 | #pred Alpha\r |
| 614 | #pred Beta\r |
| 615 | \r |
| 616 | rule1: <<Alpha>>? A\r |
| 617 | | rule2\r |
| 618 | ;\r |
| 619 | \r |
| 620 | rule2: <<Alpha>>? A\r |
| 621 | | <<Beta>>? B\r |
| 622 | ;\r |
| 623 | \r |
| 624 | The predicate used for alt 2 of rule1 is (Alpha || Beta). This\r |
| 625 | appears to be different than the predicate Alpha used for alt1.\r |
| 626 | However, the context of Beta is B. Thus when the lookahead is A\r |
| 627 | Beta will have no resolving power and Alpha will be used for both\r |
| 628 | alternatives. Using the same predicate for both alternatives isn't\r |
| 629 | very helpful, but this will not be detected with 1.33MR11.\r |
| 630 | \r |
| 631 | To properly handle this the predicate expression would have to be\r |
| 632 | evaluated for each distinct lookahead context.\r |
| 633 | \r |
| 634 | To determine whether two predicate expressions are identical is\r |
| 635 | difficult. The routine may fail to identify identical predicates.\r |
| 636 | \r |
| 637 | The #pred feature also compares predicates to see if a choice between\r |
| 638 | alternatives which is resolved by a predicate which makes the second\r |
| 639 | choice unreachable. Consider the following example:\r |
| 640 | \r |
| 641 | #pred A <<A(LATEXT(1)>>?\r |
| 642 | #pred B <<B(LATEXT(1)>>?\r |
| 643 | #pred A_or_B A || B\r |
| 644 | \r |
| 645 | r : s\r |
| 646 | | t\r |
| 647 | ;\r |
| 648 | s : <<A_or_B>>? ID\r |
| 649 | ;\r |
| 650 | t : <<A>>? ID\r |
| 651 | ;\r |
| 652 | \r |
| 653 | ----------------------------------------------------------------------------\r |
| 654 | t11.g, line 5: warning: the predicate used to disambiguate the\r |
| 655 | first choice of rule r\r |
| 656 | (file t11.g alt 1 line 5 and alt 2 line 6)\r |
| 657 | appears to "cover" the second predicate when compared without context.\r |
| 658 | The second predicate may have no resolving power for some lookahead\r |
| 659 | sequences.\r |
| 660 | ----------------------------------------------------------------------------\r |
| 661 | \r |
| 662 | #132. (Changed in 1.33MR11) Recognition of identical predicates in alts\r |
| 663 | \r |
| 664 | Prior to 1.33MR11, there would be no ambiguity warning when the\r |
| 665 | very same predicate was used to disambiguate both alternatives:\r |
| 666 | \r |
| 667 | test: ref B\r |
| 668 | | ref C\r |
| 669 | ;\r |
| 670 | \r |
| 671 | ref : <<pred(LATEXT(1)>>? A\r |
| 672 | \r |
| 673 | In 1.33MR11 this will cause the warning:\r |
| 674 | \r |
| 675 | warning: the predicates used to disambiguate rule test\r |
| 676 | (file v98.g alt 1 line 1 and alt 2 line 2)\r |
| 677 | are identical and have no resolving power\r |
| 678 | \r |
| 679 | ----------------- Note -----------------\r |
| 680 | \r |
| 681 | This is different than the following case\r |
| 682 | \r |
| 683 | test: <<pred(LATEXT(1))>>? A B\r |
| 684 | | <<pred(LATEXT(1)>>? A C\r |
| 685 | ;\r |
| 686 | \r |
| 687 | In this case there are two distinct predicates\r |
| 688 | which have exactly the same text. In the first\r |
| 689 | example there are two references to the same\r |
| 690 | predicate. The problem represented by this\r |
| 691 | grammar will be addressed later.\r |
| 692 | \r |
| 693 | \r |
| 694 | #127. (Changed in 1.33MR11)\r |
| 695 | \r |
| 696 | Count Syntax Errors Count DLG Errors\r |
| 697 | ------------------- ----------------\r |
| 698 | \r |
| 699 | C++ mode ANTLRParser:: DLGLexerBase::\r |
| 700 | syntaxErrCount lexErrCount\r |
| 701 | C mode zzSyntaxErrCount zzLexErrCount\r |
| 702 | \r |
| 703 | The C mode variables are global and initialized to 0.\r |
| 704 | They are *not* reset to 0 automatically when antlr is\r |
| 705 | restarted.\r |
| 706 | \r |
| 707 | The C++ mode variables are public. They are initialized\r |
| 708 | to 0 by the constructors. They are *not* reset to 0 by the\r |
| 709 | ANTLRParser::init() method.\r |
| 710 | \r |
| 711 | Suggested by Reinier van den Born (reinier@vnet.ibm.com).\r |
| 712 | \r |
| 713 | #126. (Changed in 1.33MR11) Addition of #first <<...>>\r |
| 714 | \r |
| 715 | The #first <<...>> inserts the specified text in the output\r |
| 716 | files before any other #include statements required by pccts.\r |
| 717 | The only things before the #first text are comments and\r |
| 718 | a #define ANTLR_VERSION.\r |
| 719 | \r |
| 720 | Requested by and Esa Pulkkinen (esap@cs.tut.fi) and Alexin\r |
| 721 | Zoltan (alexin@inf.u-szeged.hu).\r |
| 722 | \r |
| 723 | #124. A Note on the New "&&" Style Guarded Predicates\r |
| 724 | \r |
| 725 | I've been asked several times, "What is the difference between\r |
| 726 | the old "=>" style guard predicates and the new style "&&" guard\r |
| 727 | predicates, and how do you choose one over the other" ?\r |
| 728 | \r |
| 729 | The main difference is that the "=>" does not apply the\r |
| 730 | predicate if the context guard doesn't match, whereas\r |
| 731 | the && form always does. What is the significance ?\r |
| 732 | \r |
| 733 | If you have a predicate which is not on the "leading edge"\r |
| 734 | it is cannot be hoisted. Suppose you need a predicate that\r |
| 735 | looks at LA(2). You must introduce it manually. The\r |
| 736 | classic example is:\r |
| 737 | \r |
| 738 | castExpr :\r |
| 739 | LP typeName RP\r |
| 740 | | ....\r |
| 741 | ;\r |
| 742 | \r |
| 743 | typeName : <<isTypeName(LATEXT(1))>>? ID\r |
| 744 | | STRUCT ID\r |
| 745 | ;\r |
| 746 | \r |
| 747 | The problem is that isTypeName() isn't on the leading edge\r |
| 748 | of typeName, so it won't be hoisted into castExpr to help\r |
| 749 | make a decision on which production to choose.\r |
| 750 | \r |
| 751 | The *first* attempt to fix it is this:\r |
| 752 | \r |
| 753 | castExpr :\r |
| 754 | <<isTypeName(LATEXT(2))>>?\r |
| 755 | LP typeName RP\r |
| 756 | | ....\r |
| 757 | ;\r |
| 758 | \r |
| 759 | Unfortunately, this won't work because it ignores\r |
| 760 | the problem of STRUCT. The solution is to apply\r |
| 761 | isTypeName() in castExpr if LA(2) is an ID and\r |
| 762 | don't apply it when LA(2) is STRUCT:\r |
| 763 | \r |
| 764 | castExpr :\r |
| 765 | (LP ID)? => <<isTypeName(LATEXT(2))>>?\r |
| 766 | LP typeName RP\r |
| 767 | | ....\r |
| 768 | ;\r |
| 769 | \r |
| 770 | In conclusion, the "=>" style guarded predicate is\r |
| 771 | useful when:\r |
| 772 | \r |
| 773 | a. the tokens required for the predicate\r |
| 774 | are not on the leading edge\r |
| 775 | b. there are alternatives in the expression\r |
| 776 | selected by the predicate for which the\r |
| 777 | predicate is inappropriate\r |
| 778 | \r |
| 779 | If (b) were false, then one could use a simple\r |
| 780 | predicate (assuming "-prc on"):\r |
| 781 | \r |
| 782 | castExpr :\r |
| 783 | <<isTypeName(LATEXT(2))>>?\r |
| 784 | LP typeName RP\r |
| 785 | | ....\r |
| 786 | ;\r |
| 787 | \r |
| 788 | typeName : <<isTypeName(LATEXT(1))>>? ID\r |
| 789 | ;\r |
| 790 | \r |
| 791 | So, when do you use the "&&" style guarded predicate ?\r |
| 792 | \r |
| 793 | The new-style "&&" predicate should always be used with\r |
| 794 | predicate context. The context guard is in ADDITION to\r |
| 795 | the automatically computed context. Thus it useful for\r |
| 796 | predicates which depend on the token type for reasons\r |
| 797 | other than context.\r |
| 798 | \r |
| 799 | The following example is contributed by Reinier van den Born\r |
| 800 | (reinier@vnet.ibm.com).\r |
| 801 | \r |
| 802 | +-------------------------------------------------------------------------+\r |
| 803 | | This grammar has two ways to call functions: |\r |
| 804 | | |\r |
| 805 | | - a "standard" call syntax with parens and comma separated args |\r |
| 806 | | - a shell command like syntax (no parens and spacing separated args) |\r |
| 807 | | |\r |
| 808 | | The former also allows a variable to hold the name of the function, |\r |
| 809 | | the latter can also be used to call external commands. |\r |
| 810 | | |\r |
| 811 | | The grammar (simplified) looks like this: |\r |
| 812 | | |\r |
| 813 | | fun_call : ID "(" { expr ("," expr)* } ")" |\r |
| 814 | | /* ID is function name */ |\r |
| 815 | | | "@" ID "(" { expr ("," expr)* } ")" |\r |
| 816 | | /* ID is var containing fun name */ |\r |
| 817 | | ; |\r |
| 818 | | |\r |
| 819 | | command : ID expr* /* ID is function name */ |\r |
| 820 | | | path expr* /* path is external command name */ |\r |
| 821 | | ; |\r |
| 822 | | |\r |
| 823 | | path : ID /* left out slashes and such */ |\r |
| 824 | | | "@" ID /* ID is environment var */ |\r |
| 825 | | ; |\r |
| 826 | | |\r |
| 827 | | expr : .... |\r |
| 828 | | | "(" expr ")"; |\r |
| 829 | | |\r |
| 830 | | call : fun_call |\r |
| 831 | | | command |\r |
| 832 | | ; |\r |
| 833 | | |\r |
| 834 | | Obviously the call is wildly ambiguous. This is more or less how this |\r |
| 835 | | is to be resolved: |\r |
| 836 | | |\r |
| 837 | | A call begins with an ID or an @ followed by an ID. |\r |
| 838 | | |\r |
| 839 | | If it is an ID and if it is an ext. command name -> command |\r |
| 840 | | if followed by a paren -> fun_call |\r |
| 841 | | otherwise -> command |\r |
| 842 | | |\r |
| 843 | | If it is an @ and if the ID is a var name -> fun_call |\r |
| 844 | | otherwise -> command |\r |
| 845 | | |\r |
| 846 | | One can implement these rules quite neatly using && predicates: |\r |
| 847 | | |\r |
| 848 | | call : ("@" ID)? && <<isVarName(LT(2))>>? fun_call |\r |
| 849 | | | (ID)? && <<isExtCmdName>>? command |\r |
| 850 | | | (ID "(")? fun_call |\r |
| 851 | | | command |\r |
| 852 | | ; |\r |
| 853 | | |\r |
| 854 | | This can be done better, so it is not an ideal example, but it |\r |
| 855 | | conveys the principle. |\r |
| 856 | +-------------------------------------------------------------------------+\r |
| 857 | \r |
| 858 | #122. (Changed in 1.33MR11) Member functions to reset DLG in C++ mode\r |
| 859 | \r |
| 860 | void DLGFileReset(FILE *f) { input = f; found_eof = 0; }\r |
| 861 | void DLGStringReset(DLGChar *s) { input = s; p = &input[0]; }\r |
| 862 | \r |
| 863 | Supplied by R.A. Nelson (cowboy@VNET.IBM.COM)\r |
| 864 | \r |
| 865 | #119. (Changed in 1.33MR11) Ambiguity aid for grammars\r |
| 866 | \r |
| 867 | The user can ask for additional information on ambiguities reported\r |
| 868 | by antlr to stdout. At the moment, only one ambiguity report can\r |
| 869 | be created in an antlr run.\r |
| 870 | \r |
| 871 | This feature is enabled using the "-aa" (Ambiguity Aid) option.\r |
| 872 | \r |
| 873 | The following options control the reporting of ambiguities:\r |
| 874 | \r |
| 875 | -aa ruleName Selects reporting by name of rule\r |
| 876 | -aa lineNumber Selects reporting by line number\r |
| 877 | (file name not compared)\r |
| 878 | \r |
| 879 | -aam Selects "multiple" reporting for a token\r |
| 880 | in the intersection set of the\r |
| 881 | alternatives.\r |
| 882 | \r |
| 883 | For instance, the token ID may appear dozens\r |
| 884 | of times in various paths as the program\r |
| 885 | explores the rules which are reachable from\r |
| 886 | the point of an ambiguity. With option -aam\r |
| 887 | every possible path the search program\r |
| 888 | encounters is reported.\r |
| 889 | \r |
| 890 | Without -aam only the first encounter is\r |
| 891 | reported. This may result in incomplete\r |
| 892 | information, but the information may be\r |
| 893 | sufficient and much shorter.\r |
| 894 | \r |
| 895 | -aad depth Selects the depth of the search.\r |
| 896 | The default value is 1.\r |
| 897 | \r |
| 898 | The number of paths to be searched, and the\r |
| 899 | size of the report can grow geometrically\r |
| 900 | with the -ck value if a full search for all\r |
| 901 | contributions to the source of the ambiguity\r |
| 902 | is explored.\r |
| 903 | \r |
| 904 | The depth represents the number of tokens\r |
| 905 | in the lookahead set which are matched against\r |
| 906 | the set of ambiguous tokens. A depth of 1\r |
| 907 | means that the search stops when a lookahead\r |
| 908 | sequence of just one token is matched.\r |
| 909 | \r |
| 910 | A k=1 ck=6 grammar might generate 5,000 items\r |
| 911 | in a report if a full depth 6 search is made\r |
| 912 | with the Ambiguity Aid. The source of the\r |
| 913 | problem may be in the first token and obscured\r |
| 914 | by the volume of data - I hesitate to call\r |
| 915 | it information.\r |
| 916 | \r |
| 917 | When the user selects a depth > 1, the search\r |
| 918 | is first performed at depth=1 for both\r |
| 919 | alternatives, then depth=2 for both alternatives,\r |
| 920 | etc.\r |
| 921 | \r |
| 922 | Sample output for rule grammar in antlr.g itself:\r |
| 923 | \r |
| 924 | +---------------------------------------------------------------------+\r |
| 925 | | Ambiguity Aid |\r |
| 926 | | |\r |
| 927 | | Choice 1: grammar/70 line 632 file a.g |\r |
| 928 | | Choice 2: grammar/82 line 644 file a.g |\r |
| 929 | | |\r |
| 930 | | Intersection of lookahead[1] sets: |\r |
| 931 | | |\r |
| 932 | | "\}" "class" "#errclass" "#tokclass" |\r |
| 933 | | |\r |
| 934 | | Choice:1 Depth:1 Group:1 ("#errclass") |\r |
| 935 | | 1 in (...)* block grammar/70 line 632 a.g |\r |
| 936 | | 2 to error grammar/73 line 635 a.g |\r |
| 937 | | 3 error error/1 line 894 a.g |\r |
| 938 | | 4 #token "#errclass" error/2 line 895 a.g |\r |
| 939 | | |\r |
| 940 | | Choice:1 Depth:1 Group:2 ("#tokclass") |\r |
| 941 | | 2 to tclass grammar/74 line 636 a.g |\r |
| 942 | | 3 tclass tclass/1 line 937 a.g |\r |
| 943 | | 4 #token "#tokclass" tclass/2 line 938 a.g |\r |
| 944 | | |\r |
| 945 | | Choice:1 Depth:1 Group:3 ("class") |\r |
| 946 | | 2 to class_def grammar/75 line 637 a.g |\r |
| 947 | | 3 class_def class_def/1 line 669 a.g |\r |
| 948 | | 4 #token "class" class_def/3 line 671 a.g |\r |
| 949 | | |\r |
| 950 | | Choice:1 Depth:1 Group:4 ("\}") |\r |
| 951 | | 2 #token "\}" grammar/76 line 638 a.g |\r |
| 952 | | |\r |
| 953 | | Choice:2 Depth:1 Group:5 ("#errclass") |\r |
| 954 | | 1 in (...)* block grammar/83 line 645 a.g |\r |
| 955 | | 2 to error grammar/93 line 655 a.g |\r |
| 956 | | 3 error error/1 line 894 a.g |\r |
| 957 | | 4 #token "#errclass" error/2 line 895 a.g |\r |
| 958 | | |\r |
| 959 | | Choice:2 Depth:1 Group:6 ("#tokclass") |\r |
| 960 | | 2 to tclass grammar/94 line 656 a.g |\r |
| 961 | | 3 tclass tclass/1 line 937 a.g |\r |
| 962 | | 4 #token "#tokclass" tclass/2 line 938 a.g |\r |
| 963 | | |\r |
| 964 | | Choice:2 Depth:1 Group:7 ("class") |\r |
| 965 | | 2 to class_def grammar/95 line 657 a.g |\r |
| 966 | | 3 class_def class_def/1 line 669 a.g |\r |
| 967 | | 4 #token "class" class_def/3 line 671 a.g |\r |
| 968 | | |\r |
| 969 | | Choice:2 Depth:1 Group:8 ("\}") |\r |
| 970 | | 2 #token "\}" grammar/96 line 658 a.g |\r |
| 971 | +---------------------------------------------------------------------+\r |
| 972 | \r |
| 973 | For a linear lookahead set ambiguity (where k=1 or for k>1 but\r |
| 974 | when all lookahead sets [i] with i<k all have degree one) the\r |
| 975 | reports appear in the following order:\r |
| 976 | \r |
| 977 | for (depth=1 ; depth <= "-aad depth" ; depth++) {\r |
| 978 | for (alternative=1; alternative <=2 ; alternative++) {\r |
| 979 | while (matches-are-found) {\r |
| 980 | group++;\r |
| 981 | print-report\r |
| 982 | };\r |
| 983 | };\r |
| 984 | };\r |
| 985 | \r |
| 986 | For reporting a k-tuple ambiguity, the reports appear in the\r |
| 987 | following order:\r |
| 988 | \r |
| 989 | for (depth=1 ; depth <= "-aad depth" ; depth++) {\r |
| 990 | while (matches-are-found) {\r |
| 991 | for (alternative=1; alternative <=2 ; alternative++) {\r |
| 992 | group++;\r |
| 993 | print-report\r |
| 994 | };\r |
| 995 | };\r |
| 996 | };\r |
| 997 | \r |
| 998 | This is because matches are generated in different ways for\r |
| 999 | linear lookahead and k-tuples.\r |
| 1000 | \r |
| 1001 | #117. (Changed in 1.33MR10) new EXPERIMENTAL predicate hoisting code\r |
| 1002 | \r |
| 1003 | The hoisting of predicates into rules to create prediction\r |
| 1004 | expressions is a problem in antlr. Consider the following\r |
| 1005 | example (k=1 with -prc on):\r |
| 1006 | \r |
| 1007 | start : (a)* "@" ;\r |
| 1008 | a : b | c ;\r |
| 1009 | b : <<isUpper(LATEXT(1))>>? A ;\r |
| 1010 | c : A ;\r |
| 1011 | \r |
| 1012 | Prior to 1.33MR10 the code generated for "start" would resemble:\r |
| 1013 | \r |
| 1014 | while {\r |
| 1015 | if (LA(1)==A &&\r |
| 1016 | (!LA(1)==A || isUpper())) {\r |
| 1017 | a();\r |
| 1018 | }\r |
| 1019 | };\r |
| 1020 | \r |
| 1021 | This code is wrong because it makes rule "c" unreachable from\r |
| 1022 | "start". The essence of the problem is that antlr fails to\r |
| 1023 | recognize that there can be a valid alternative within "a" even\r |
| 1024 | when the predicate <<isUpper(LATEXT(1))>>? is false.\r |
| 1025 | \r |
| 1026 | In 1.33MR10 with -mrhoist the hoisting of the predicate into\r |
| 1027 | "start" is suppressed because it recognizes that "c" can\r |
| 1028 | cover all the cases where the predicate is false:\r |
| 1029 | \r |
| 1030 | while {\r |
| 1031 | if (LA(1)==A) {\r |
| 1032 | a();\r |
| 1033 | }\r |
| 1034 | };\r |
| 1035 | \r |
| 1036 | With the antlr "-info p" switch the user will receive information\r |
| 1037 | about the predicate suppression in the generated file:\r |
| 1038 | \r |
| 1039 | --------------------------------------------------------------\r |
| 1040 | #if 0\r |
| 1041 | \r |
| 1042 | Hoisting of predicate suppressed by alternative without predicate.\r |
| 1043 | The alt without the predicate includes all cases where\r |
| 1044 | the predicate is false.\r |
| 1045 | \r |
| 1046 | WITH predicate: line 7 v1.g\r |
| 1047 | WITHOUT predicate: line 7 v1.g\r |
| 1048 | \r |
| 1049 | The context set for the predicate:\r |
| 1050 | \r |
| 1051 | A\r |
| 1052 | \r |
| 1053 | The lookahead set for the alt WITHOUT the semantic predicate:\r |
| 1054 | \r |
| 1055 | A\r |
| 1056 | \r |
| 1057 | The predicate:\r |
| 1058 | \r |
| 1059 | pred << isUpper(LATEXT(1))>>?\r |
| 1060 | depth=k=1 rule b line 9 v1.g\r |
| 1061 | set context:\r |
| 1062 | A\r |
| 1063 | tree context: null\r |
| 1064 | \r |
| 1065 | Chain of referenced rules:\r |
| 1066 | \r |
| 1067 | #0 in rule start (line 5 v1.g) to rule a\r |
| 1068 | #1 in rule a (line 7 v1.g)\r |
| 1069 | \r |
| 1070 | #endif\r |
| 1071 | --------------------------------------------------------------\r |
| 1072 | \r |
| 1073 | A predicate can be suppressed by a combination of alternatives\r |
| 1074 | which, taken together, cover a predicate:\r |
| 1075 | \r |
| 1076 | start : (a)* "@" ;\r |
| 1077 | \r |
| 1078 | a : b | ca | cb | cc ;\r |
| 1079 | \r |
| 1080 | b : <<isUpper(LATEXT(1))>>? ( A | B | C ) ;\r |
| 1081 | \r |
| 1082 | ca : A ;\r |
| 1083 | cb : B ;\r |
| 1084 | cc : C ;\r |
| 1085 | \r |
| 1086 | Consider a more complex example in which "c" covers only part of\r |
| 1087 | a predicate:\r |
| 1088 | \r |
| 1089 | start : (a)* "@" ;\r |
| 1090 | \r |
| 1091 | a : b\r |
| 1092 | | c\r |
| 1093 | ;\r |
| 1094 | \r |
| 1095 | b : <<isUpper(LATEXT(1))>>?\r |
| 1096 | ( A\r |
| 1097 | | X\r |
| 1098 | );\r |
| 1099 | \r |
| 1100 | c : A\r |
| 1101 | ;\r |
| 1102 | \r |
| 1103 | Prior to 1.33MR10 the code generated for "start" would resemble:\r |
| 1104 | \r |
| 1105 | while {\r |
| 1106 | if ( (LA(1)==A || LA(1)==X) &&\r |
| 1107 | (! (LA(1)==A || LA(1)==X) || isUpper()) {\r |
| 1108 | a();\r |
| 1109 | }\r |
| 1110 | };\r |
| 1111 | \r |
| 1112 | With 1.33MR10 and -mrhoist the predicate context is restricted to\r |
| 1113 | the non-covered lookahead. The code resembles:\r |
| 1114 | \r |
| 1115 | while {\r |
| 1116 | if ( (LA(1)==A || LA(1)==X) &&\r |
| 1117 | (! (LA(1)==X) || isUpper()) {\r |
| 1118 | a();\r |
| 1119 | }\r |
| 1120 | };\r |
| 1121 | \r |
| 1122 | With the antlr "-info p" switch the user will receive information\r |
| 1123 | about the predicate restriction in the generated file:\r |
| 1124 | \r |
| 1125 | --------------------------------------------------------------\r |
| 1126 | #if 0\r |
| 1127 | \r |
| 1128 | Restricting the context of a predicate because of overlap\r |
| 1129 | in the lookahead set between the alternative with the\r |
| 1130 | semantic predicate and one without\r |
| 1131 | Without this restriction the alternative without the predicate\r |
| 1132 | could not be reached when input matched the context of the\r |
| 1133 | predicate and the predicate was false.\r |
| 1134 | \r |
| 1135 | WITH predicate: line 11 v4.g\r |
| 1136 | WITHOUT predicate: line 12 v4.g\r |
| 1137 | \r |
| 1138 | The original context set for the predicate:\r |
| 1139 | \r |
| 1140 | A X\r |
| 1141 | \r |
| 1142 | The lookahead set for the alt WITHOUT the semantic predicate:\r |
| 1143 | \r |
| 1144 | A\r |
| 1145 | \r |
| 1146 | The intersection of the two sets\r |
| 1147 | \r |
| 1148 | A\r |
| 1149 | \r |
| 1150 | The original predicate:\r |
| 1151 | \r |
| 1152 | pred << isUpper(LATEXT(1))>>?\r |
| 1153 | depth=k=1 rule b line 15 v4.g\r |
| 1154 | set context:\r |
| 1155 | A X\r |
| 1156 | tree context: null\r |
| 1157 | \r |
| 1158 | The new (modified) form of the predicate:\r |
| 1159 | \r |
| 1160 | pred << isUpper(LATEXT(1))>>?\r |
| 1161 | depth=k=1 rule b line 15 v4.g\r |
| 1162 | set context:\r |
| 1163 | X\r |
| 1164 | tree context: null\r |
| 1165 | \r |
| 1166 | #endif\r |
| 1167 | --------------------------------------------------------------\r |
| 1168 | \r |
| 1169 | The bad news about -mrhoist:\r |
| 1170 | \r |
| 1171 | (a) -mrhoist does not analyze predicates with lookahead\r |
| 1172 | depth > 1.\r |
| 1173 | \r |
| 1174 | (b) -mrhoist does not look past a guarded predicate to\r |
| 1175 | find context which might cover other predicates.\r |
| 1176 | \r |
| 1177 | For these cases you might want to use syntactic predicates.\r |
| 1178 | When a semantic predicate fails during guess mode the guess\r |
| 1179 | fails and the next alternative is tried.\r |
| 1180 | \r |
| 1181 | Limitation (a) is illustrated by the following example:\r |
| 1182 | \r |
| 1183 | start : (stmt)* EOF ;\r |
| 1184 | \r |
| 1185 | stmt : cast\r |
| 1186 | | expr\r |
| 1187 | ;\r |
| 1188 | cast : <<isTypename(LATEXT(2))>>? LP ID RP ;\r |
| 1189 | \r |
| 1190 | expr : LP ID RP ;\r |
| 1191 | \r |
| 1192 | This is not much different from the first example, except that\r |
| 1193 | it requires two tokens of lookahead context to determine what\r |
| 1194 | to do. This predicate is NOT suppressed because the current version\r |
| 1195 | is unable to handle predicates with depth > 1.\r |
| 1196 | \r |
| 1197 | A predicate can be combined with other predicates during hoisting.\r |
| 1198 | In those cases the depth=1 predicates are still handled. Thus,\r |
| 1199 | in the following example the isUpper() predicate will be suppressed\r |
| 1200 | by line #4 when hoisted from "bizarre" into "start", but will still\r |
| 1201 | be present in "bizarre" in order to predict "stmt".\r |
| 1202 | \r |
| 1203 | start : (bizarre)* EOF ; // #1\r |
| 1204 | // #2\r |
| 1205 | bizarre : stmt // #3\r |
| 1206 | | A // #4\r |
| 1207 | ;\r |
| 1208 | \r |
| 1209 | stmt : cast\r |
| 1210 | | expr\r |
| 1211 | ;\r |
| 1212 | \r |
| 1213 | cast : <<isTypename(LATEXT(2))>>? LP ID RP ;\r |
| 1214 | \r |
| 1215 | expr : LP ID RP ;\r |
| 1216 | | <<isUpper(LATEXT(1))>>? A\r |
| 1217 | \r |
| 1218 | Limitation (b) is illustrated by the following example of a\r |
| 1219 | context guarded predicate:\r |
| 1220 | \r |
| 1221 | rule : (A)? <<p>>? // #1\r |
| 1222 | (A // #2\r |
| 1223 | |B // #3\r |
| 1224 | ) // #4\r |
| 1225 | | <<q>> B // #5\r |
| 1226 | ;\r |
| 1227 | \r |
| 1228 | Recall that this means that when the lookahead is NOT A then\r |
| 1229 | the predicate "p" is ignored and it attempts to match "A|B".\r |
| 1230 | Ideally, the "B" at line #3 should suppress predicate "q".\r |
| 1231 | However, the current version does not attempt to look past\r |
| 1232 | the guard predicate to find context which might suppress other\r |
| 1233 | predicates.\r |
| 1234 | \r |
| 1235 | In some cases -mrhoist will lead to the reporting of ambiguities\r |
| 1236 | which were not visible before:\r |
| 1237 | \r |
| 1238 | start : (a)* "@";\r |
| 1239 | a : bc | d;\r |
| 1240 | bc : b | c ;\r |
| 1241 | \r |
| 1242 | b : <<isUpper(LATEXT(1))>>? A;\r |
| 1243 | c : A ;\r |
| 1244 | \r |
| 1245 | d : A ;\r |
| 1246 | \r |
| 1247 | In this case there is a true ambiguity in "a" between "bc" and "d"\r |
| 1248 | which can both match "A". Without -mrhoist the predicate in "b"\r |
| 1249 | is hoisted into "a" and there is no ambiguity reported. However,\r |
| 1250 | with -mrhoist, the predicate in "b" is suppressed by "c" (as it\r |
| 1251 | should be) making the ambiguity in "a" apparent.\r |
| 1252 | \r |
| 1253 | The motivations for these changes were hoisting problems reported\r |
| 1254 | by Reinier van den Born (reinier@vnet.ibm.com) and several others.\r |
| 1255 | \r |
| 1256 | #113. (Changed in 1.33MR10) new context guarded pred: (g)? && <<p>>? expr\r |
| 1257 | \r |
| 1258 | The existing context guarded predicate:\r |
| 1259 | \r |
| 1260 | rule : (guard)? => <<p>>? expr\r |
| 1261 | | next_alternative\r |
| 1262 | ;\r |
| 1263 | \r |
| 1264 | generates code which resembles:\r |
| 1265 | \r |
| 1266 | if (lookahead(expr) && (!guard || pred)) {\r |
| 1267 | expr()\r |
| 1268 | } else ....\r |
| 1269 | \r |
| 1270 | This is not suitable for some applications because it allows\r |
| 1271 | expr() to be invoked when the predicate is false. This is\r |
| 1272 | intentional because it is meant to mimic automatically computed\r |
| 1273 | predicate context.\r |
| 1274 | \r |
| 1275 | The new context guarded predicate uses the guard information\r |
| 1276 | differently because it has a different goal. Consider:\r |
| 1277 | \r |
| 1278 | rule : (guard)? && <<p>>? expr\r |
| 1279 | | next_alternative\r |
| 1280 | ;\r |
| 1281 | \r |
| 1282 | The new style of context guarded predicate is equivalent to:\r |
| 1283 | \r |
| 1284 | rule : <<guard==true && pred>>? expr\r |
| 1285 | | next_alternative\r |
| 1286 | ;\r |
| 1287 | \r |
| 1288 | It generates code which resembles:\r |
| 1289 | \r |
| 1290 | if (lookahead(expr) && guard && pred) {\r |
| 1291 | expr();\r |
| 1292 | } else ...\r |
| 1293 | \r |
| 1294 | Both forms of guarded predicates severely restrict the form of\r |
| 1295 | the context guard: it can contain no rule references, no\r |
| 1296 | (...)*, no (...)+, and no {...}. It may contain token and\r |
| 1297 | token class references, and alternation ("|").\r |
| 1298 | \r |
| 1299 | Addition for 1.33MR11: in the token expression all tokens must\r |
| 1300 | be at the same height of the token tree:\r |
| 1301 | \r |
| 1302 | (A ( B | C))? && ... is ok (all height 2)\r |
| 1303 | (A ( B | ))? && ... is not ok (some 1, some 2)\r |
| 1304 | (A B C D | E F G H)? && ... is ok (all height 4)\r |
| 1305 | (A B C D | E )? && ... is not ok (some 4, some 1)\r |
| 1306 | \r |
| 1307 | This restriction is required in order to properly compute the lookahead\r |
| 1308 | set for expressions like:\r |
| 1309 | \r |
| 1310 | rule1 : (A B C)? && <<pred>>? rule2 ;\r |
| 1311 | rule2 : (A|X) (B|Y) (C|Z);\r |
| 1312 | \r |
| 1313 | This addition was suggested by Rienier van den Born (reinier@vnet.ibm.com)\r |
| 1314 | \r |
| 1315 | #109. (Changed in 1.33MR10) improved trace information\r |
| 1316 | \r |
| 1317 | The quality of the trace information provided by the "-gd"\r |
| 1318 | switch has been improved significantly. Here is an example\r |
| 1319 | of the output from a test program. It shows the rule name,\r |
| 1320 | the first token of lookahead, the call depth, and the guess\r |
| 1321 | status:\r |
| 1322 | \r |
| 1323 | exit rule gusxx {"?"} depth 2\r |
| 1324 | enter rule gusxx {"?"} depth 2\r |
| 1325 | enter rule gus1 {"o"} depth 3 guessing\r |
| 1326 | guess done - returning to rule gus1 {"o"} at depth 3\r |
| 1327 | (guess mode continues - an enclosing guess is still active)\r |
| 1328 | guess done - returning to rule gus1 {"Z"} at depth 3\r |
| 1329 | (guess mode continues - an enclosing guess is still active)\r |
| 1330 | exit rule gus1 {"Z"} depth 3 guessing\r |
| 1331 | guess done - returning to rule gusxx {"o"} at depth 2 (guess mode ends)\r |
| 1332 | enter rule gus1 {"o"} depth 3\r |
| 1333 | guess done - returning to rule gus1 {"o"} at depth 3 (guess mode ends)\r |
| 1334 | guess done - returning to rule gus1 {"Z"} at depth 3 (guess mode ends)\r |
| 1335 | exit rule gus1 {"Z"} depth 3\r |
| 1336 | line 1: syntax error at "Z" missing SC\r |
| 1337 | ...\r |
| 1338 | \r |
| 1339 | Rule trace reporting is controlled by the value of the integer\r |
| 1340 | [zz]traceOptionValue: when it is positive tracing is enabled,\r |
| 1341 | otherwise it is disabled. Tracing during guess mode is controlled\r |
| 1342 | by the value of the integer [zz]traceGuessOptionValue. When\r |
| 1343 | it is positive AND [zz]traceOptionValue is positive rule trace\r |
| 1344 | is reported in guess mode.\r |
| 1345 | \r |
| 1346 | The values of [zz]traceOptionValue and [zz]traceGuessOptionValue\r |
| 1347 | can be adjusted by subroutine calls listed below.\r |
| 1348 | \r |
| 1349 | Depending on the presence or absence of the antlr -gd switch\r |
| 1350 | the variable [zz]traceOptionValueDefault is set to 0 or 1. When\r |
| 1351 | the parser is initialized or [zz]traceReset() is called the\r |
| 1352 | value of [zz]traceOptionValueDefault is copied to [zz]traceOptionValue.\r |
| 1353 | The value of [zz]traceGuessOptionValue is always initialzed to 1,\r |
| 1354 | but, as noted earlier, nothing will be reported unless\r |
| 1355 | [zz]traceOptionValue is also positive.\r |
| 1356 | \r |
| 1357 | When the parser state is saved/restored the value of the trace\r |
| 1358 | variables are also saved/restored. If a restore causes a change in\r |
| 1359 | reporting behavior from on to off or vice versa this will be reported.\r |
| 1360 | \r |
| 1361 | When the -gd option is selected, the macro "#define zzTRACE_RULES"\r |
| 1362 | is added to appropriate output files.\r |
| 1363 | \r |
| 1364 | C++ mode\r |
| 1365 | --------\r |
| 1366 | int traceOption(int delta)\r |
| 1367 | int traceGuessOption(int delta)\r |
| 1368 | void traceReset()\r |
| 1369 | int traceOptionValueDefault\r |
| 1370 | \r |
| 1371 | C mode\r |
| 1372 | --------\r |
| 1373 | int zzTraceOption(int delta)\r |
| 1374 | int zzTraceGuessOption(int delta)\r |
| 1375 | void zzTraceReset()\r |
| 1376 | int zzTraceOptionValueDefault\r |
| 1377 | \r |
| 1378 | The argument "delta" is added to the traceOptionValue. To\r |
| 1379 | turn on trace when inside a particular rule one:\r |
| 1380 | \r |
| 1381 | rule : <<traceOption(+1);>>\r |
| 1382 | (\r |
| 1383 | rest-of-rule\r |
| 1384 | )\r |
| 1385 | <<traceOption(-1);>>\r |
| 1386 | ; /* fail clause */ <<traceOption(-1);>>\r |
| 1387 | \r |
| 1388 | One can use the same idea to turn *off* tracing within a\r |
| 1389 | rule by using a delta of (-1).\r |
| 1390 | \r |
| 1391 | An improvement in the rule trace was suggested by Sramji\r |
| 1392 | Ramanathan (ps@kumaran.com).\r |
| 1393 | \r |
| 1394 | #108. A Note on Deallocation of Variables Allocated in Guess Mode\r |
| 1395 | \r |
| 1396 | NOTE\r |
| 1397 | ------------------------------------------------------\r |
| 1398 | This mechanism only works for heap allocated variables\r |
| 1399 | ------------------------------------------------------\r |
| 1400 | \r |
| 1401 | The rewrite of the trace provides the machinery necessary\r |
| 1402 | to properly free variables or undo actions following a\r |
| 1403 | failed guess.\r |
| 1404 | \r |
| 1405 | The macro zzUSER_GUESS_HOOK(guessSeq,zzrv) is expanded\r |
| 1406 | as part of the zzGUESS macro. When a guess is opened\r |
| 1407 | the value of zzrv is 0. When a longjmp() is executed to\r |
| 1408 | undo the guess, the value of zzrv will be 1.\r |
| 1409 | \r |
| 1410 | The macro zzUSER_GUESS_DONE_HOOK(guessSeq) is expanded\r |
| 1411 | as part of the zzGUESS_DONE macro. This is executed\r |
| 1412 | whether the guess succeeds or fails as part of closing\r |
| 1413 | the guess.\r |
| 1414 | \r |
| 1415 | The guessSeq is a sequence number which is assigned to each\r |
| 1416 | guess and is incremented by 1 for each guess which becomes\r |
| 1417 | active. It is needed by the user to associate the start of\r |
| 1418 | a guess with the failure and/or completion (closing) of a\r |
| 1419 | guess.\r |
| 1420 | \r |
| 1421 | Guesses are nested. They must be closed in the reverse\r |
| 1422 | of the order that they are opened.\r |
| 1423 | \r |
| 1424 | In order to free memory used by a variable during a guess\r |
| 1425 | a user must write a routine which can be called to\r |
| 1426 | register the variable along with the current guess sequence\r |
| 1427 | number provided by the zzUSER_GUESS_HOOK macro. If the guess\r |
| 1428 | fails, all variables tagged with the corresponding guess\r |
| 1429 | sequence number should be released. This is ugly, but\r |
| 1430 | it would require a major rewrite of antlr 1.33 to use\r |
| 1431 | some mechanism other than setjmp()/longjmp().\r |
| 1432 | \r |
| 1433 | The order of calls for a *successful* guess would be:\r |
| 1434 | \r |
| 1435 | zzUSER_GUESS_HOOK(guessSeq,0);\r |
| 1436 | zzUSER_GUESS_DONE_HOOK(guessSeq);\r |
| 1437 | \r |
| 1438 | The order of calls for a *failed* guess would be:\r |
| 1439 | \r |
| 1440 | zzUSER_GUESS_HOOK(guessSeq,0);\r |
| 1441 | zzUSER_GUESS_HOOK(guessSeq,1);\r |
| 1442 | zzUSER_GUESS_DONE_HOOK(guessSeq);\r |
| 1443 | \r |
| 1444 | The default definitions of these macros are empty strings.\r |
| 1445 | \r |
| 1446 | Here is an example in C++ mode. The zzUSER_GUESS_HOOK and\r |
| 1447 | zzUSER_GUESS_DONE_HOOK macros and myGuessHook() routine\r |
| 1448 | can be used without change in both C and C++ versions.\r |
| 1449 | \r |
| 1450 | ----------------------------------------------------------------------\r |
| 1451 | <<\r |
| 1452 | \r |
| 1453 | #include "AToken.h"\r |
| 1454 | \r |
| 1455 | typedef ANTLRCommonToken ANTLRToken;\r |
| 1456 | \r |
| 1457 | #include "DLGLexer.h"\r |
| 1458 | \r |
| 1459 | int main() {\r |
| 1460 | \r |
| 1461 | {\r |
| 1462 | DLGFileInput in(stdin);\r |
| 1463 | DLGLexer lexer(&in,2000);\r |
| 1464 | ANTLRTokenBuffer pipe(&lexer,1);\r |
| 1465 | ANTLRCommonToken aToken;\r |
| 1466 | P parser(&pipe);\r |
| 1467 | \r |
| 1468 | lexer.setToken(&aToken);\r |
| 1469 | parser.init();\r |
| 1470 | parser.start();\r |
| 1471 | };\r |
| 1472 | \r |
| 1473 | fclose(stdin);\r |
| 1474 | fclose(stdout);\r |
| 1475 | return 0;\r |
| 1476 | }\r |
| 1477 | \r |
| 1478 | >>\r |
| 1479 | \r |
| 1480 | <<\r |
| 1481 | char *s=NULL;\r |
| 1482 | \r |
| 1483 | #undef zzUSER_GUESS_HOOK\r |
| 1484 | #define zzUSER_GUESS_HOOK(guessSeq,zzrv) myGuessHook(guessSeq,zzrv);\r |
| 1485 | #undef zzUSER_GUESS_DONE_HOOK\r |
| 1486 | #define zzUSER_GUESS_DONE_HOOK(guessSeq) myGuessHook(guessSeq,2);\r |
| 1487 | \r |
| 1488 | void myGuessHook(int guessSeq,int zzrv) {\r |
| 1489 | if (zzrv == 0) {\r |
| 1490 | fprintf(stderr,"User hook: starting guess #%d\n",guessSeq);\r |
| 1491 | } else if (zzrv == 1) {\r |
| 1492 | free (s);\r |
| 1493 | s=NULL;\r |
| 1494 | fprintf(stderr,"User hook: failed guess #%d\n",guessSeq);\r |
| 1495 | } else if (zzrv == 2) {\r |
| 1496 | free (s);\r |
| 1497 | s=NULL;\r |
| 1498 | fprintf(stderr,"User hook: ending guess #%d\n",guessSeq);\r |
| 1499 | };\r |
| 1500 | }\r |
| 1501 | \r |
| 1502 | >>\r |
| 1503 | \r |
| 1504 | #token A "a"\r |
| 1505 | #token "[\t \ \n]" <<skip();>>\r |
| 1506 | \r |
| 1507 | class P {\r |
| 1508 | \r |
| 1509 | start : (top)+\r |
| 1510 | ;\r |
| 1511 | \r |
| 1512 | top : (which) ? <<fprintf(stderr,"%s is a which\n",s); free(s); s=NULL; >>\r |
| 1513 | | other <<fprintf(stderr,"%s is an other\n",s); free(s); s=NULL; >>\r |
| 1514 | ; <<if (s != NULL) free(s); s=NULL; >>\r |
| 1515 | \r |
| 1516 | which : which2\r |
| 1517 | ;\r |
| 1518 | \r |
| 1519 | which2 : which3\r |
| 1520 | ;\r |
| 1521 | which3\r |
| 1522 | : (label)? <<fprintf(stderr,"%s is a label\n",s);>>\r |
| 1523 | | (global)? <<fprintf(stderr,"%s is a global\n",s);>>\r |
| 1524 | | (exclamation)? <<fprintf(stderr,"%s is an exclamation\n",s);>>\r |
| 1525 | ;\r |
| 1526 | \r |
| 1527 | label : <<s=strdup(LT(1)->getText());>> A ":" ;\r |
| 1528 | \r |
| 1529 | global : <<s=strdup(LT(1)->getText());>> A "::" ;\r |
| 1530 | \r |
| 1531 | exclamation : <<s=strdup(LT(1)->getText());>> A "!" ;\r |
| 1532 | \r |
| 1533 | other : <<s=strdup(LT(1)->getText());>> "other" ;\r |
| 1534 | \r |
| 1535 | }\r |
| 1536 | ----------------------------------------------------------------------\r |
| 1537 | \r |
| 1538 | This is a silly example, but illustrates the idea. For the input\r |
| 1539 | "a ::" with tracing enabled the output begins:\r |
| 1540 | \r |
| 1541 | ----------------------------------------------------------------------\r |
| 1542 | enter rule "start" depth 1\r |
| 1543 | enter rule "top" depth 2\r |
| 1544 | User hook: starting guess #1\r |
| 1545 | enter rule "which" depth 3 guessing\r |
| 1546 | enter rule "which2" depth 4 guessing\r |
| 1547 | enter rule "which3" depth 5 guessing\r |
| 1548 | User hook: starting guess #2\r |
| 1549 | enter rule "label" depth 6 guessing\r |
| 1550 | guess failed\r |
| 1551 | User hook: failed guess #2\r |
| 1552 | guess done - returning to rule "which3" at depth 5 (guess mode continues\r |
| 1553 | - an enclosing guess is still active)\r |
| 1554 | User hook: ending guess #2\r |
| 1555 | User hook: starting guess #3\r |
| 1556 | enter rule "global" depth 6 guessing\r |
| 1557 | exit rule "global" depth 6 guessing\r |
| 1558 | guess done - returning to rule "which3" at depth 5 (guess mode continues\r |
| 1559 | - an enclosing guess is still active)\r |
| 1560 | User hook: ending guess #3\r |
| 1561 | enter rule "global" depth 6 guessing\r |
| 1562 | exit rule "global" depth 6 guessing\r |
| 1563 | exit rule "which3" depth 5 guessing\r |
| 1564 | exit rule "which2" depth 4 guessing\r |
| 1565 | exit rule "which" depth 3 guessing\r |
| 1566 | guess done - returning to rule "top" at depth 2 (guess mode ends)\r |
| 1567 | User hook: ending guess #1\r |
| 1568 | enter rule "which" depth 3\r |
| 1569 | .....\r |
| 1570 | ----------------------------------------------------------------------\r |
| 1571 | \r |
| 1572 | Remember:\r |
| 1573 | \r |
| 1574 | (a) Only init-actions are executed during guess mode.\r |
| 1575 | (b) A rule can be invoked multiple times during guess mode.\r |
| 1576 | (c) If the guess succeeds the rule will be called once more\r |
| 1577 | without guess mode so that normal actions will be executed.\r |
| 1578 | This means that the init-action might need to distinguish\r |
| 1579 | between guess mode and non-guess mode using the variable\r |
| 1580 | [zz]guessing.\r |
| 1581 | \r |
| 1582 | #101. (Changed in 1.33MR10) antlr -info command line switch\r |
| 1583 | \r |
| 1584 | -info\r |
| 1585 | \r |
| 1586 | p - extra predicate information in generated file\r |
| 1587 | \r |
| 1588 | t - information about tnode use:\r |
| 1589 | at the end of each rule in generated file\r |
| 1590 | summary on stderr at end of program\r |
| 1591 | \r |
| 1592 | m - monitor progress\r |
| 1593 | prints name of each rule as it is started\r |
| 1594 | flushes output at start of each rule\r |
| 1595 | \r |
| 1596 | f - first/follow set information to stdout\r |
| 1597 | \r |
| 1598 | 0 - no operation (added in 1.33MR11)\r |
| 1599 | \r |
| 1600 | The options may be combined and may appear in any order.\r |
| 1601 | For example:\r |
| 1602 | \r |
| 1603 | antlr -info ptm -CC -gt -mrhoist on mygrammar.g\r |
| 1604 | \r |
| 1605 | #100a. (Changed in 1.33MR10) Predicate tree simplification\r |
| 1606 | \r |
| 1607 | When the same predicates can be referenced in more than one\r |
| 1608 | alternative of a block large predicate trees can be formed.\r |
| 1609 | \r |
| 1610 | The difference that these optimizations make is so dramatic\r |
| 1611 | that I have decided to use it even when -mrhoist is not selected.\r |
| 1612 | \r |
| 1613 | Consider the following grammar:\r |
| 1614 | \r |
| 1615 | start : ( all )* ;\r |
| 1616 | \r |
| 1617 | all : a\r |
| 1618 | | d\r |
| 1619 | | e\r |
| 1620 | | f\r |
| 1621 | ;\r |
| 1622 | \r |
| 1623 | a : c A B\r |
| 1624 | | c A C\r |
| 1625 | ;\r |
| 1626 | \r |
| 1627 | c : <<AAA(LATEXT(2))>>?\r |
| 1628 | ;\r |
| 1629 | \r |
| 1630 | d : <<BBB(LATEXT(2))>>? B C\r |
| 1631 | ;\r |
| 1632 | \r |
| 1633 | e : <<CCC(LATEXT(2))>>? B C\r |
| 1634 | ;\r |
| 1635 | \r |
| 1636 | f : e X Y\r |
| 1637 | ;\r |
| 1638 | \r |
| 1639 | In rule "a" there is a reference to rule "c" in both alternatives.\r |
| 1640 | The length of the predicate AAA is k=2 and it can be followed in\r |
| 1641 | alternative 1 only by (A B) while in alternative 2 it can be\r |
| 1642 | followed only by (A C). Thus they do not have identical context.\r |
| 1643 | \r |
| 1644 | In rule "all" the alternatives which refer to rules "e" and "f" allow\r |
| 1645 | elimination of the duplicate reference to predicate CCC.\r |
| 1646 | \r |
| 1647 | The table below summarized the kind of simplification performed by\r |
| 1648 | 1.33MR10. In the table, X and Y stand for single predicates\r |
| 1649 | (not trees).\r |
| 1650 | \r |
| 1651 | (OR X (OR Y (OR Z))) => (OR X Y Z)\r |
| 1652 | (AND X (AND Y (AND Z))) => (AND X Y Z)\r |
| 1653 | \r |
| 1654 | (OR X (... (OR X Y) ... )) => (OR X (... Y ... ))\r |
| 1655 | (AND X (... (AND X Y) ... )) => (AND X (... Y ... ))\r |
| 1656 | (OR X (... (AND X Y) ... )) => (OR X (... ... ))\r |
| 1657 | (AND X (... (OR X Y) ... )) => (AND X (... ... ))\r |
| 1658 | \r |
| 1659 | (AND X) => X\r |
| 1660 | (OR X) => X\r |
| 1661 | \r |
| 1662 | In a test with a complex grammar for a real application, a predicate\r |
| 1663 | tree with six OR nodes and 12 leaves was reduced to "(OR X Y Z)".\r |
| 1664 | \r |
| 1665 | In 1.33MR10 there is a greater effort to release memory used\r |
| 1666 | by predicates once they are no longer in use.\r |
| 1667 | \r |
| 1668 | #100b. (Changed in 1.33MR10) Suppression of extra predicate tests\r |
| 1669 | \r |
| 1670 | The following optimizations require that -mrhoist be selected.\r |
| 1671 | \r |
| 1672 | It is relatively easy to optimize the code generated for predicate\r |
| 1673 | gates when they are of the form:\r |
| 1674 | \r |
| 1675 | (AND X Y Z ...)\r |
| 1676 | or (OR X Y Z ...)\r |
| 1677 | \r |
| 1678 | where X, Y, Z, and "..." represent individual predicates (leaves) not\r |
| 1679 | predicate trees.\r |
| 1680 | \r |
| 1681 | If the predicate is an AND the contexts of the X, Y, Z, etc. are\r |
| 1682 | ANDed together to create a single Tree context for the group and\r |
| 1683 | context tests for the individual predicates are suppressed:\r |
| 1684 | \r |
| 1685 | --------------------------------------------------\r |
| 1686 | Note: This was incorrect. The contexts should be\r |
| 1687 | ORed together. This has been fixed. A more \r |
| 1688 | complete description is available in item #152.\r |
| 1689 | ---------------------------------------------------\r |
| 1690 | \r |
| 1691 | Optimization 1: (AND X Y Z ...)\r |
| 1692 | \r |
| 1693 | Suppose the context for Xtest is LA(1)==LP and the context for\r |
| 1694 | Ytest is LA(1)==LP && LA(2)==ID.\r |
| 1695 | \r |
| 1696 | Without the optimization the code would resemble:\r |
| 1697 | \r |
| 1698 | if (lookaheadContext &&\r |
| 1699 | !(LA(1)==LP && LA(1)==LP && LA(2)==ID) ||\r |
| 1700 | ( (! LA(1)==LP || Xtest) &&\r |
| 1701 | (! (LA(1)==LP || LA(2)==ID) || Xtest)\r |
| 1702 | )) {...\r |
| 1703 | \r |
| 1704 | With the -mrhoist optimization the code would resemble:\r |
| 1705 | \r |
| 1706 | if (lookaheadContext &&\r |
| 1707 | ! (LA(1)==LP && LA(2)==ID) || (Xtest && Ytest) {...\r |
| 1708 | \r |
| 1709 | Optimization 2: (OR X Y Z ...) with identical contexts\r |
| 1710 | \r |
| 1711 | Suppose the context for Xtest is LA(1)==ID and for Ytest\r |
| 1712 | the context is also LA(1)==ID.\r |
| 1713 | \r |
| 1714 | Without the optimization the code would resemble:\r |
| 1715 | \r |
| 1716 | if (lookaheadContext &&\r |
| 1717 | ! (LA(1)==ID || LA(1)==ID) ||\r |
| 1718 | (LA(1)==ID && Xtest) ||\r |
| 1719 | (LA(1)==ID && Ytest) {...\r |
| 1720 | \r |
| 1721 | With the -mrhoist optimization the code would resemble:\r |
| 1722 | \r |
| 1723 | if (lookaheadContext &&\r |
| 1724 | (! LA(1)==ID) || (Xtest || Ytest) {...\r |
| 1725 | \r |
| 1726 | Optimization 3: (OR X Y Z ...) with distinct contexts\r |
| 1727 | \r |
| 1728 | Suppose the context for Xtest is LA(1)==ID and for Ytest\r |
| 1729 | the context is LA(1)==LP.\r |
| 1730 | \r |
| 1731 | Without the optimization the code would resemble:\r |
| 1732 | \r |
| 1733 | if (lookaheadContext &&\r |
| 1734 | ! (LA(1)==ID || LA(1)==LP) ||\r |
| 1735 | (LA(1)==ID && Xtest) ||\r |
| 1736 | (LA(1)==LP && Ytest) {...\r |
| 1737 | \r |
| 1738 | With the -mrhoist optimization the code would resemble:\r |
| 1739 | \r |
| 1740 | if (lookaheadContext &&\r |
| 1741 | (zzpf=0,\r |
| 1742 | (LA(1)==ID && (zzpf=1) && Xtest) ||\r |
| 1743 | (LA(1)==LP && (zzpf=1) && Ytest) ||\r |
| 1744 | !zzpf) {\r |
| 1745 | \r |
| 1746 | These may appear to be of similar complexity at first,\r |
| 1747 | but the non-optimized version contains two tests of each\r |
| 1748 | context while the optimized version contains only one\r |
| 1749 | such test, as well as eliminating some of the inverted\r |
| 1750 | logic (" !(...) || ").\r |
| 1751 | \r |
| 1752 | Optimization 4: Computation of predicate gate trees\r |
| 1753 | \r |
| 1754 | When generating code for the gates of predicate expressions\r |
| 1755 | antlr 1.33 vanilla uses a recursive procedure to generate\r |
| 1756 | "&&" and "||" expressions for testing the lookahead. As each\r |
| 1757 | layer of the predicate tree is exposed a new set of "&&" and\r |
| 1758 | "||" expressions on the lookahead are generated. In many\r |
| 1759 | cases the lookahead being tested has already been tested.\r |
| 1760 | \r |
| 1761 | With -mrhoist a lookahead tree is computed for the entire\r |
| 1762 | lookahead expression. This means that predicates with identical\r |
| 1763 | context or context which is a subset of another predicate's\r |
| 1764 | context disappear.\r |
| 1765 | \r |
| 1766 | This is especially important for predicates formed by rules\r |
| 1767 | like the following:\r |
| 1768 | \r |
| 1769 | uppperCaseVowel : <<isUpperCase(LATEXT(1))>>? vowel;\r |
| 1770 | vowel: : <<isVowel(LATEXT(1))>>? LETTERS;\r |
| 1771 | \r |
| 1772 | These predicates are combined using AND since both must be\r |
| 1773 | satisfied for rule upperCaseVowel. They have identical\r |
| 1774 | context which makes this optimization very effective.\r |
| 1775 | \r |
| 1776 | The affect of Items #100a and #100b together can be dramatic. In\r |
| 1777 | a very large (but real world) grammar one particular predicate\r |
| 1778 | expression was reduced from an (unreadable) 50 predicate leaves,\r |
| 1779 | 195 LA(1) terms, and 5500 characters to an (easily comprehensible)\r |
| 1780 | 3 predicate leaves (all different) and a *single* LA(1) term.\r |
| 1781 | \r |
| 1782 | #98. (Changed in 1.33MR10) Option "-info p"\r |
| 1783 | \r |
| 1784 | When the user selects option "-info p" the program will generate\r |
| 1785 | detailed information about predicates. If the user selects\r |
| 1786 | "-mrhoist on" additional detail will be provided explaining\r |
| 1787 | the promotion and suppression of predicates. The output is part\r |
| 1788 | of the generated file and sandwiched between #if 0/#endif statements.\r |
| 1789 | \r |
| 1790 | Consider the following k=1 grammar:\r |
| 1791 | \r |
| 1792 | start : ( all ) * ;\r |
| 1793 | \r |
| 1794 | all : ( a\r |
| 1795 | | b\r |
| 1796 | )\r |
| 1797 | ;\r |
| 1798 | \r |
| 1799 | a : c B\r |
| 1800 | ;\r |
| 1801 | \r |
| 1802 | c : <<LATEXT(1)>>?\r |
| 1803 | | B\r |
| 1804 | ;\r |
| 1805 | \r |
| 1806 | b : <<LATEXT(1)>>? X\r |
| 1807 | ;\r |
| 1808 | \r |
| 1809 | Below is an excerpt of the output for rule "start" for the three\r |
| 1810 | predicate options (off, on, and maintenance release style hoisting).\r |
| 1811 | \r |
| 1812 | For those who do not wish to use the "-mrhoist on" option for code\r |
| 1813 | generation the option can be used in a "diagnostic" mode to provide\r |
| 1814 | valuable information:\r |
| 1815 | \r |
| 1816 | a. where one should insert null actions to inhibit hoisting\r |
| 1817 | b. a chain of rule references which shows where predicates are\r |
| 1818 | being hoisted\r |
| 1819 | \r |
| 1820 | ======================================================================\r |
| 1821 | Example of "-info p" with "-mrhoist on"\r |
| 1822 | ======================================================================\r |
| 1823 | #if 0\r |
| 1824 | \r |
| 1825 | Hoisting of predicate suppressed by alternative without predicate.\r |
| 1826 | The alt without the predicate includes all cases where the\r |
| 1827 | predicate is false.\r |
| 1828 | \r |
| 1829 | WITH predicate: line 11 v36.g\r |
| 1830 | WITHOUT predicate: line 12 v36.g\r |
| 1831 | \r |
| 1832 | The context set for the predicate:\r |
| 1833 | \r |
| 1834 | B\r |
| 1835 | \r |
| 1836 | The lookahead set for alt WITHOUT the semantic predicate:\r |
| 1837 | \r |
| 1838 | B\r |
| 1839 | \r |
| 1840 | The predicate:\r |
| 1841 | \r |
| 1842 | pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r |
| 1843 | \r |
| 1844 | set context:\r |
| 1845 | B\r |
| 1846 | tree context: null\r |
| 1847 | \r |
| 1848 | Chain of referenced rules:\r |
| 1849 | \r |
| 1850 | #0 in rule start (line 1 v36.g) to rule all\r |
| 1851 | #1 in rule all (line 3 v36.g) to rule a\r |
| 1852 | #2 in rule a (line 8 v36.g) to rule c\r |
| 1853 | #3 in rule c (line 11 v36.g)\r |
| 1854 | \r |
| 1855 | #endif\r |
| 1856 | &&\r |
| 1857 | #if 0\r |
| 1858 | \r |
| 1859 | pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r |
| 1860 | \r |
| 1861 | set context:\r |
| 1862 | X\r |
| 1863 | tree context: null\r |
| 1864 | \r |
| 1865 | #endif\r |
| 1866 | ======================================================================\r |
| 1867 | Example of "-info p" with the default -prc setting ( "-prc off")\r |
| 1868 | ======================================================================\r |
| 1869 | #if 0\r |
| 1870 | \r |
| 1871 | OR\r |
| 1872 | pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r |
| 1873 | \r |
| 1874 | set context:\r |
| 1875 | nil\r |
| 1876 | tree context: null\r |
| 1877 | \r |
| 1878 | pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r |
| 1879 | \r |
| 1880 | set context:\r |
| 1881 | nil\r |
| 1882 | tree context: null\r |
| 1883 | \r |
| 1884 | #endif\r |
| 1885 | ======================================================================\r |
| 1886 | Example of "-info p" with "-prc on" and "-mrhoist off"\r |
| 1887 | ======================================================================\r |
| 1888 | #if 0\r |
| 1889 | \r |
| 1890 | OR\r |
| 1891 | pred << LATEXT(1)>>? depth=k=1 rule c line 11 v36.g\r |
| 1892 | \r |
| 1893 | set context:\r |
| 1894 | B\r |
| 1895 | tree context: null\r |
| 1896 | \r |
| 1897 | pred << LATEXT(1)>>? depth=k=1 rule b line 15 v36.g\r |
| 1898 | \r |
| 1899 | set context:\r |
| 1900 | X\r |
| 1901 | tree context: null\r |
| 1902 | \r |
| 1903 | #endif\r |
| 1904 | ======================================================================\r |
| 1905 | \r |
| 1906 | #60. (Changed in 1.33MR7) Major changes to exception handling\r |
| 1907 | \r |
| 1908 | There were significant problems in the handling of exceptions\r |
| 1909 | in 1.33 vanilla. The general problem is that it can only\r |
| 1910 | process one level of exception handler. For example, a named\r |
| 1911 | exception handler, an exception handler for an alternative, or\r |
| 1912 | an exception for a subrule always went to the rule's exception\r |
| 1913 | handler if there was no "catch" which matched the exception.\r |
| 1914 | \r |
| 1915 | In 1.33MR7 the exception handlers properly "nest". If an\r |
| 1916 | exception handler does not have a matching "catch" then the\r |
| 1917 | nextmost outer exception handler is checked for an appropriate\r |
| 1918 | "catch" clause, and so on until an exception handler with an\r |
| 1919 | appropriate "catch" is found.\r |
| 1920 | \r |
| 1921 | There are still undesirable features in the way exception\r |
| 1922 | handlers are implemented, but I do not have time to fix them\r |
| 1923 | at the moment:\r |
| 1924 | \r |
| 1925 | The exception handlers for alternatives are outside the\r |
| 1926 | block containing the alternative. This makes it impossible\r |
| 1927 | to access variables declared in a block or to resume the\r |
| 1928 | parse by "falling through". The parse can still be easily\r |
| 1929 | resumed in other ways, but not in the most natural fashion.\r |
| 1930 | \r |
| 1931 | This results in an inconsistentcy between named exception\r |
| 1932 | handlers and exception handlers for alternatives. When\r |
| 1933 | an exception handler for an alternative "falls through"\r |
| 1934 | it goes to the nextmost outer handler - not the "normal\r |
| 1935 | action".\r |
| 1936 | \r |
| 1937 | A major difference between 1.33MR7 and 1.33 vanilla is\r |
| 1938 | the default action after an exception is caught:\r |
| 1939 | \r |
| 1940 | 1.33 Vanilla\r |
| 1941 | ------------\r |
| 1942 | In 1.33 vanilla the signal value is set to zero ("NoSignal")\r |
| 1943 | and the code drops through to the code following the exception.\r |
| 1944 | For named exception handlers this is the "normal action".\r |
| 1945 | For alternative exception handlers this is the rule's handler.\r |
| 1946 | \r |
| 1947 | 1.33MR7\r |
| 1948 | -------\r |
| 1949 | In 1.33MR7 the signal value is NOT automatically set to zero.\r |
| 1950 | \r |
| 1951 | There are two cases:\r |
| 1952 | \r |
| 1953 | For named exception handlers: if the signal value has been\r |
| 1954 | set to zero the code drops through to the "normal action".\r |
| 1955 | \r |
| 1956 | For all other cases the code branches to the nextmost outer\r |
| 1957 | exception handler until it reaches the handler for the rule.\r |
| 1958 | \r |
| 1959 | The following macros have been defined for convenience:\r |
| 1960 | \r |
| 1961 | C/C++ Mode Name\r |
| 1962 | --------------------\r |
| 1963 | (zz)suppressSignal\r |
| 1964 | set signal & return signal arg to 0 ("NoSignal")\r |
| 1965 | (zz)setSignal(intValue)\r |
| 1966 | set signal & return signal arg to some value\r |
| 1967 | (zz)exportSignal\r |
| 1968 | copy the signal value to the return signal arg\r |
| 1969 | \r |
| 1970 | I'm not sure why PCCTS make a distinction between the local\r |
| 1971 | signal value and the return signal argument, but I'm loathe\r |
| 1972 | to change the code. The burden of copying the local signal\r |
| 1973 | value to the return signal argument can be given to the\r |
| 1974 | default signal handler, I suppose.\r |
| 1975 | \r |
| 1976 | #53. (Explanation for 1.33MR6) What happens after an exception is caught ?\r |
| 1977 | \r |
| 1978 | The Book is silent about what happens after an exception\r |
| 1979 | is caught.\r |
| 1980 | \r |
| 1981 | The following code fragment prints "Error Action" followed\r |
| 1982 | by "Normal Action".\r |
| 1983 | \r |
| 1984 | test : Word ex:Number <<printf("Normal Action\n");>>\r |
| 1985 | exception[ex]\r |
| 1986 | catch NoViableAlt:\r |
| 1987 | <<printf("Error Action\n");>>\r |
| 1988 | ;\r |
| 1989 | \r |
| 1990 | The reason for "Normal Action" is that the normal flow of the\r |
| 1991 | program after a user-written exception handler is to "drop through".\r |
| 1992 | In the case of an exception handler for a rule this results in\r |
| 1993 | the exection of a "return" statement. In the case of an\r |
| 1994 | exception handler attached to an alternative, rule, or token\r |
| 1995 | this is the code that would have executed had there been no\r |
| 1996 | exception.\r |
| 1997 | \r |
| 1998 | The user can achieve the desired result by using a "return"\r |
| 1999 | statement.\r |
| 2000 | \r |
| 2001 | test : Word ex:Number <<printf("Normal Action\n");>>\r |
| 2002 | exception[ex]\r |
| 2003 | catch NoViableAlt:\r |
| 2004 | <<printf("Error Action\n"); return;>>\r |
| 2005 | ;\r |
| 2006 | \r |
| 2007 | The most powerful mechanism for recovery from parse errors\r |
| 2008 | in pccts is syntactic predicates because they provide\r |
| 2009 | backtracking. Exceptions allow "return", "break",\r |
| 2010 | "consumeUntil(...)", "goto _handler", "goto _fail", and\r |
| 2011 | changing the _signal value.\r |
| 2012 | \r |
| 2013 | #41. (Added in 1.33MR6) antlr -stdout\r |
| 2014 | \r |
| 2015 | Using "antlr -stdout ..." forces the text that would\r |
| 2016 | normally go to the grammar.c or grammar.cpp file to\r |
| 2017 | stdout.\r |
| 2018 | \r |
| 2019 | #40. (Added in 1.33MR6) antlr -tab to change tab stops\r |
| 2020 | \r |
| 2021 | Using "antlr -tab number ..." changes the tab stops\r |
| 2022 | for the grammar.c or grammar.cpp file. The number\r |
| 2023 | must be between 0 and 8. Using 0 gives tab characters,\r |
| 2024 | values between 1 and 8 give the appropriate number of\r |
| 2025 | space characters.\r |
| 2026 | \r |
| 2027 | #34. (Added to 1.33MR1) Add public DLGLexerBase::set_line(int newValue)\r |
| 2028 | \r |
| 2029 | Previously there was no public function for changing the line\r |
| 2030 | number maintained by the lexer.\r |
| 2031 | \r |
| 2032 | #28. (Added to 1.33MR1) More control over DLG header\r |
| 2033 | \r |
| 2034 | Version 1.33MR1 adds the following directives to PCCTS\r |
| 2035 | for C++ mode:\r |
| 2036 | \r |
| 2037 | #lexprefix <<source code>>\r |
| 2038 | \r |
| 2039 | Adds source code to the DLGLexer.h file\r |
| 2040 | after the #include "DLexerBase.h" but\r |
| 2041 | before the start of the class definition.\r |
| 2042 | \r |
| 2043 | #lexmember <<source code>>\r |
| 2044 | \r |
| 2045 | Adds source code to the DLGLexer.h file\r |
| 2046 | as part of the DLGLexer class body. It\r |
| 2047 | appears immediately after the start of\r |
| 2048 | the class and a "public: statement.\r |
| 2049 | \r |
projects / mirror_edk2.git / blame