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Date: Wed, 22 Dec 2004 03:00:10 -0500
From: William Lovas <wlovas@stwing.upenn.edu>
To: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Str.string_match incorrect
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On Tue, Dec 21, 2004 at 11:44:55PM -0800, Evan Martin wrote:
> This is consistent with the docs, which say:
>   [string_match r s start] tests whether the characters in s starting at
>   position start match the regular expression r.
> and in general with how regular expression systems work.  string_match
> corresponds to running your automaton directly and seeing whether you
> end up in an accept state, while string_partial_match effectively adds
> an extra ".*" to the beginning.
> (It's more debatable whether this makes sense.)

I concur with your assessment, but i think you're characterization of the
semantics of string_partial_match is inaccurate:

    # Str.string_match (Str.regexp "ab") "a" 0;;
    - : bool = false
    # Str.string_partial_match (Str.regexp "ab") "a" 0;;
    - : bool = true
    # Str.string_match (Str.regexp ".*ab") "a" 0;;
    - : bool = false

... unless of course, i've misunderstood you.  I don't think there's a
simple transformation on regular expressions that allow you to emulate
string_partial_match's behavior using only string_match.  (Does anyone
care to prove me wrong? :)

cheers,
William