Mercurial > cpython-lru_cache-weakref
annotate Parser/parser.c @ 25838:8540887bcec6 2.2
Backport of 2.183:
Fix memory leak in add_subclass() found by NealN with valgrind.
| author | Guido van Rossum <guido@python.org> |
|---|---|
| date | Fri, 18 Oct 2002 13:42:21 +0000 |
| parents | 944d6e02f359 |
| children | 1db1510abe21 |
| rev | line source |
|---|---|
| 145 | 1 |
| 6 | 2 /* Parser implementation */ |
| 3 | |
| 4 /* For a description, see the comments at end of this file */ | |
| 5 | |
| 6 /* XXX To do: error recovery */ | |
| 7 | |
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8 #include "Python.h" |
| 86 | 9 #include "pgenheaders.h" |
| 6 | 10 #include "token.h" |
| 11 #include "grammar.h" | |
| 12 #include "node.h" | |
| 13 #include "parser.h" | |
| 14 #include "errcode.h" | |
| 15 | |
| 16 | |
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17 #ifdef Py_DEBUG |
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18 extern int Py_DebugFlag; |
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19 #define D(x) if (!Py_DebugFlag); else x |
| 6 | 20 #else |
| 21 #define D(x) | |
| 22 #endif | |
| 23 | |
| 24 | |
| 25 /* STACK DATA TYPE */ | |
| 26 | |
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27 static void s_reset(stack *); |
| 6 | 28 |
| 29 static void | |
| 13659 | 30 s_reset(stack *s) |
| 6 | 31 { |
| 32 s->s_top = &s->s_base[MAXSTACK]; | |
| 33 } | |
| 34 | |
| 35 #define s_empty(s) ((s)->s_top == &(s)->s_base[MAXSTACK]) | |
| 36 | |
| 37 static int | |
| 13659 | 38 s_push(register stack *s, dfa *d, node *parent) |
| 6 | 39 { |
| 40 register stackentry *top; | |
| 41 if (s->s_top == s->s_base) { | |
| 42 fprintf(stderr, "s_push: parser stack overflow\n"); | |
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43 return E_NOMEM; |
| 6 | 44 } |
| 45 top = --s->s_top; | |
| 46 top->s_dfa = d; | |
| 47 top->s_parent = parent; | |
| 48 top->s_state = 0; | |
| 49 return 0; | |
| 50 } | |
| 51 | |
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52 #ifdef Py_DEBUG |
| 6 | 53 |
| 54 static void | |
| 13659 | 55 s_pop(register stack *s) |
| 6 | 56 { |
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57 if (s_empty(s)) |
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58 Py_FatalError("s_pop: parser stack underflow -- FATAL"); |
| 6 | 59 s->s_top++; |
| 60 } | |
| 61 | |
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62 #else /* !Py_DEBUG */ |
| 6 | 63 |
| 64 #define s_pop(s) (s)->s_top++ | |
| 65 | |
| 66 #endif | |
| 67 | |
| 68 | |
| 69 /* PARSER CREATION */ | |
| 70 | |
| 71 parser_state * | |
| 13659 | 72 PyParser_New(grammar *g, int start) |
| 6 | 73 { |
| 74 parser_state *ps; | |
| 75 | |
| 76 if (!g->g_accel) | |
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77 PyGrammar_AddAccelerators(g); |
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78 ps = PyMem_NEW(parser_state, 1); |
| 6 | 79 if (ps == NULL) |
| 80 return NULL; | |
| 81 ps->p_grammar = g; | |
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82 ps->p_generators = 0; |
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83 ps->p_tree = PyNode_New(start); |
| 6 | 84 if (ps->p_tree == NULL) { |
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85 PyMem_DEL(ps); |
| 6 | 86 return NULL; |
| 87 } | |
| 88 s_reset(&ps->p_stack); | |
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89 (void) s_push(&ps->p_stack, PyGrammar_FindDFA(g, start), ps->p_tree); |
| 6 | 90 return ps; |
| 91 } | |
| 92 | |
| 93 void | |
| 13659 | 94 PyParser_Delete(parser_state *ps) |
| 6 | 95 { |
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96 /* NB If you want to save the parse tree, |
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97 you must set p_tree to NULL before calling delparser! */ |
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98 PyNode_Free(ps->p_tree); |
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99 PyMem_DEL(ps); |
| 6 | 100 } |
| 101 | |
| 102 | |
| 103 /* PARSER STACK OPERATIONS */ | |
| 104 | |
| 105 static int | |
| 13659 | 106 shift(register stack *s, int type, char *str, int newstate, int lineno) |
| 6 | 107 { |
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108 int err; |
| 6 | 109 assert(!s_empty(s)); |
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110 err = PyNode_AddChild(s->s_top->s_parent, type, str, lineno); |
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111 if (err) |
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112 return err; |
| 6 | 113 s->s_top->s_state = newstate; |
| 114 return 0; | |
| 115 } | |
| 116 | |
| 117 static int | |
| 13659 | 118 push(register stack *s, int type, dfa *d, int newstate, int lineno) |
| 6 | 119 { |
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120 int err; |
| 6 | 121 register node *n; |
| 122 n = s->s_top->s_parent; | |
| 123 assert(!s_empty(s)); | |
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124 err = PyNode_AddChild(n, type, (char *)NULL, lineno); |
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125 if (err) |
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126 return err; |
| 6 | 127 s->s_top->s_state = newstate; |
| 128 return s_push(s, d, CHILD(n, NCH(n)-1)); | |
| 129 } | |
| 130 | |
| 131 | |
| 132 /* PARSER PROPER */ | |
| 133 | |
| 134 static int | |
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135 classify(parser_state *ps, int type, char *str) |
| 6 | 136 { |
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137 grammar *g = ps->p_grammar; |
| 6 | 138 register int n = g->g_ll.ll_nlabels; |
| 139 | |
| 140 if (type == NAME) { | |
| 141 register char *s = str; | |
| 142 register label *l = g->g_ll.ll_label; | |
| 143 register int i; | |
| 144 for (i = n; i > 0; i--, l++) { | |
| 145 if (l->lb_type == NAME && l->lb_str != NULL && | |
| 146 l->lb_str[0] == s[0] && | |
| 147 strcmp(l->lb_str, s) == 0) { | |
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148 if (!ps->p_generators && |
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149 s[0] == 'y' && |
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150 strcmp(s, "yield") == 0) |
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151 break; /* not a keyword */ |
| 6 | 152 D(printf("It's a keyword\n")); |
| 153 return n - i; | |
| 154 } | |
| 155 } | |
| 156 } | |
| 157 | |
| 158 { | |
| 159 register label *l = g->g_ll.ll_label; | |
| 160 register int i; | |
| 161 for (i = n; i > 0; i--, l++) { | |
| 162 if (l->lb_type == type && l->lb_str == NULL) { | |
| 163 D(printf("It's a token we know\n")); | |
| 164 return n - i; | |
| 165 } | |
| 166 } | |
| 167 } | |
| 168 | |
| 169 D(printf("Illegal token\n")); | |
| 170 return -1; | |
| 171 } | |
| 172 | |
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173 static void |
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174 future_hack(parser_state *ps) |
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175 { |
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176 node *n = ps->p_stack.s_top->s_parent; |
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177 node *ch; |
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178 int i; |
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179 |
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180 if (strcmp(STR(CHILD(n, 0)), "from") != 0) |
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181 return; |
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182 ch = CHILD(n, 1); |
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183 if (strcmp(STR(CHILD(ch, 0)), "__future__") != 0) |
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184 return; |
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185 for (i = 3; i < NCH(n); i += 2) { |
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186 ch = CHILD(n, i); |
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187 if (NCH(ch) >= 1 && TYPE(CHILD(ch, 0)) == NAME && |
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188 strcmp(STR(CHILD(ch, 0)), "generators") == 0) { |
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189 ps->p_generators = 1; |
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190 break; |
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191 } |
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192 } |
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193 } |
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194 |
| 6 | 195 int |
| 13659 | 196 PyParser_AddToken(register parser_state *ps, register int type, char *str, |
| 197 int lineno, int *expected_ret) | |
| 6 | 198 { |
| 199 register int ilabel; | |
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200 int err; |
| 6 | 201 |
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202 D(printf("Token %s/'%s' ... ", _PyParser_TokenNames[type], str)); |
| 6 | 203 |
| 204 /* Find out which label this token is */ | |
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205 ilabel = classify(ps, type, str); |
| 6 | 206 if (ilabel < 0) |
| 207 return E_SYNTAX; | |
| 208 | |
| 209 /* Loop until the token is shifted or an error occurred */ | |
| 210 for (;;) { | |
| 211 /* Fetch the current dfa and state */ | |
| 212 register dfa *d = ps->p_stack.s_top->s_dfa; | |
| 213 register state *s = &d->d_state[ps->p_stack.s_top->s_state]; | |
| 214 | |
| 215 D(printf(" DFA '%s', state %d:", | |
| 216 d->d_name, ps->p_stack.s_top->s_state)); | |
| 217 | |
| 218 /* Check accelerator */ | |
| 219 if (s->s_lower <= ilabel && ilabel < s->s_upper) { | |
| 220 register int x = s->s_accel[ilabel - s->s_lower]; | |
| 221 if (x != -1) { | |
| 222 if (x & (1<<7)) { | |
| 223 /* Push non-terminal */ | |
| 224 int nt = (x >> 8) + NT_OFFSET; | |
| 225 int arrow = x & ((1<<7)-1); | |
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226 dfa *d1 = PyGrammar_FindDFA( |
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227 ps->p_grammar, nt); |
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228 if ((err = push(&ps->p_stack, nt, d1, |
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229 arrow, lineno)) > 0) { |
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230 D(printf(" MemError: push\n")); |
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231 return err; |
| 6 | 232 } |
| 233 D(printf(" Push ...\n")); | |
| 234 continue; | |
| 235 } | |
| 236 | |
| 237 /* Shift the token */ | |
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238 if ((err = shift(&ps->p_stack, type, str, |
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239 x, lineno)) > 0) { |
| 6 | 240 D(printf(" MemError: shift.\n")); |
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241 return err; |
| 6 | 242 } |
| 243 D(printf(" Shift.\n")); | |
| 244 /* Pop while we are in an accept-only state */ | |
| 245 while (s = &d->d_state | |
| 246 [ps->p_stack.s_top->s_state], | |
| 247 s->s_accept && s->s_narcs == 1) { | |
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248 D(printf(" DFA '%s', state %d: " |
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249 "Direct pop.\n", |
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250 d->d_name, |
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251 ps->p_stack.s_top->s_state)); |
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252 if (d->d_name[0] == 'i' && |
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253 strcmp(d->d_name, |
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254 "import_stmt") == 0) |
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255 future_hack(ps); |
| 6 | 256 s_pop(&ps->p_stack); |
| 257 if (s_empty(&ps->p_stack)) { | |
| 258 D(printf(" ACCEPT.\n")); | |
| 259 return E_DONE; | |
| 260 } | |
| 261 d = ps->p_stack.s_top->s_dfa; | |
| 262 } | |
| 263 return E_OK; | |
| 264 } | |
| 265 } | |
| 266 | |
| 267 if (s->s_accept) { | |
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268 if (d->d_name[0] == 'i' && |
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269 strcmp(d->d_name, "import_stmt") == 0) |
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270 future_hack(ps); |
| 6 | 271 /* Pop this dfa and try again */ |
| 272 s_pop(&ps->p_stack); | |
| 273 D(printf(" Pop ...\n")); | |
| 274 if (s_empty(&ps->p_stack)) { | |
| 275 D(printf(" Error: bottom of stack.\n")); | |
| 276 return E_SYNTAX; | |
| 277 } | |
| 278 continue; | |
| 279 } | |
| 280 | |
| 281 /* Stuck, report syntax error */ | |
| 282 D(printf(" Error.\n")); | |
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283 if (expected_ret) { |
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284 if (s->s_lower == s->s_upper - 1) { |
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285 /* Only one possible expected token */ |
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286 *expected_ret = ps->p_grammar-> |
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287 g_ll.ll_label[s->s_lower].lb_type; |
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288 } |
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289 else |
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290 *expected_ret = -1; |
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291 } |
| 6 | 292 return E_SYNTAX; |
| 293 } | |
| 294 } | |
| 295 | |
| 296 | |
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297 #ifdef Py_DEBUG |
| 6 | 298 |
| 299 /* DEBUG OUTPUT */ | |
| 300 | |
| 301 void | |
| 13659 | 302 dumptree(grammar *g, node *n) |
| 6 | 303 { |
| 304 int i; | |
| 305 | |
| 306 if (n == NULL) | |
| 307 printf("NIL"); | |
| 308 else { | |
| 309 label l; | |
| 310 l.lb_type = TYPE(n); | |
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311 l.lb_str = STR(n); |
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312 printf("%s", PyGrammar_LabelRepr(&l)); |
| 6 | 313 if (ISNONTERMINAL(TYPE(n))) { |
| 314 printf("("); | |
| 315 for (i = 0; i < NCH(n); i++) { | |
| 316 if (i > 0) | |
| 317 printf(","); | |
| 318 dumptree(g, CHILD(n, i)); | |
| 319 } | |
| 320 printf(")"); | |
| 321 } | |
| 322 } | |
| 323 } | |
| 324 | |
| 325 void | |
| 13659 | 326 showtree(grammar *g, node *n) |
| 6 | 327 { |
| 328 int i; | |
| 329 | |
| 330 if (n == NULL) | |
| 331 return; | |
| 332 if (ISNONTERMINAL(TYPE(n))) { | |
| 333 for (i = 0; i < NCH(n); i++) | |
| 334 showtree(g, CHILD(n, i)); | |
| 335 } | |
| 336 else if (ISTERMINAL(TYPE(n))) { | |
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337 printf("%s", _PyParser_TokenNames[TYPE(n)]); |
| 6 | 338 if (TYPE(n) == NUMBER || TYPE(n) == NAME) |
| 339 printf("(%s)", STR(n)); | |
| 340 printf(" "); | |
| 341 } | |
| 342 else | |
| 343 printf("? "); | |
| 344 } | |
| 345 | |
| 346 void | |
| 13659 | 347 printtree(parser_state *ps) |
| 6 | 348 { |
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349 if (Py_DebugFlag) { |
| 6 | 350 printf("Parse tree:\n"); |
| 351 dumptree(ps->p_grammar, ps->p_tree); | |
| 352 printf("\n"); | |
| 353 printf("Tokens:\n"); | |
| 354 showtree(ps->p_grammar, ps->p_tree); | |
| 355 printf("\n"); | |
| 356 } | |
| 357 printf("Listing:\n"); | |
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358 PyNode_ListTree(ps->p_tree); |
| 6 | 359 printf("\n"); |
| 360 } | |
| 361 | |
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362 #endif /* Py_DEBUG */ |
| 6 | 363 |
| 364 /* | |
| 365 | |
| 366 Description | |
| 367 ----------- | |
| 368 | |
| 369 The parser's interface is different than usual: the function addtoken() | |
| 370 must be called for each token in the input. This makes it possible to | |
| 371 turn it into an incremental parsing system later. The parsing system | |
| 372 constructs a parse tree as it goes. | |
| 373 | |
| 374 A parsing rule is represented as a Deterministic Finite-state Automaton | |
| 375 (DFA). A node in a DFA represents a state of the parser; an arc represents | |
| 376 a transition. Transitions are either labeled with terminal symbols or | |
| 377 with non-terminals. When the parser decides to follow an arc labeled | |
| 378 with a non-terminal, it is invoked recursively with the DFA representing | |
| 379 the parsing rule for that as its initial state; when that DFA accepts, | |
| 380 the parser that invoked it continues. The parse tree constructed by the | |
| 381 recursively called parser is inserted as a child in the current parse tree. | |
| 382 | |
| 383 The DFA's can be constructed automatically from a more conventional | |
| 384 language description. An extended LL(1) grammar (ELL(1)) is suitable. | |
| 385 Certain restrictions make the parser's life easier: rules that can produce | |
| 386 the empty string should be outlawed (there are other ways to put loops | |
| 387 or optional parts in the language). To avoid the need to construct | |
| 388 FIRST sets, we can require that all but the last alternative of a rule | |
| 389 (really: arc going out of a DFA's state) must begin with a terminal | |
| 390 symbol. | |
| 391 | |
| 392 As an example, consider this grammar: | |
| 393 | |
| 394 expr: term (OP term)* | |
| 395 term: CONSTANT | '(' expr ')' | |
| 396 | |
| 397 The DFA corresponding to the rule for expr is: | |
| 398 | |
| 399 ------->.---term-->.-------> | |
| 400 ^ | | |
| 401 | | | |
| 402 \----OP----/ | |
| 403 | |
| 404 The parse tree generated for the input a+b is: | |
| 405 | |
| 406 (expr: (term: (NAME: a)), (OP: +), (term: (NAME: b))) | |
| 407 | |
| 408 */ |