Changeset 4085 for trunk/lispref/searching.texi
- Timestamp:
- 2006年05月18日 16時19分18秒 (3 years ago)
- Files:
-
- trunk/lispref/searching.texi (modified) (2 diffs)
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trunk/lispref/searching.texi
r4073 r4085 307 307 @samp{ar} and there is only @samp{r} left to match, so this try fails. 308 308 The next alternative is for @samp{a*} to match only two @samp{a}s. With 309 this choice, the rest of the regexp matches successfully.@refill 310 311 Nested repetition operators take a long time, or even forever, if they 309 this choice, the rest of the regexp matches successfully. 310 311 @strong{Warning:} Nested repetition operators take a long time, 312 or even forever, if they 312 313 lead to ambiguous matching. For example, trying to match the regular 313 314 expression @samp{\(x+y*\)*a} against the string … … 317 318 @samp{\(x*\)*} can match the null string in infinitely many ways, so 318 319 it causes an infinite loop. To avoid these problems, check nested 319 repetitions carefully. 320 repetitions carefully, to make sure that they do not cause combinatorial 321 explosions in backtracking. 320 322 321 323 @item @samp{+}
