]> As promised, here is a summary of the replies I got concerning the "feature poll" for OCaml's regexp library. Feature 1: back-references in regexps (e.g. "([a-z]+)\1", meaning any sequence of lowercase letters followed by another occurrence of the same sequence) use often 4 use occasionally 3 no use 5 Feature 2: partial string matching as per Str.string_partial_match, i.e. the ability to recognize that a string is a prefix of a string that match a regexp. has already used 0 could use in some cases 6 no use 8 A few more remarks on these two features, and why I asked about them in particular. Feature 1 is standard in many regexp packages because it's trivial to implement in a backtracking regexp matcher. However, it's essentially impossible to implement if the regexp is compiled down to a deterministic automata. Thus, supporting feature 1 precludes DFA-based implementations such as Jérôme Vouillon's RE library. Feature 2 is unusual and I haven't heard from anyone that uses it :-) I got two replies suggesting one plausible scenario where partial matching could come handy: find delimiters in a piece of text that is being read block by block. However, I'm not sure Str.string_partial_match is adequate here, it looks like a "search forward for a partial match" operation is needed, which Str doesn't provide... It was also suggested to me that the effect of partial matching against a regexp R can be achieved by exact matching against a regexp R' derived from R. This is true for "textbook regexps", e.g. if R is "ab*c", then R' would be "epsilon|a(epsilon|b*(epsilon|c))", but doesn't work for more complex regexps languages, especially if back-references are supported. (Consider R = "(a+)\1".) Thanks for your input, - Xavier Leroy ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners