[cl-ppcre-devel] searching backward?

[Edi Weitz]

On Fri, 16 Feb 2007 06:19:42 -0800, Shawn Betts <sabetts at vcn.bc.ca> wrote:

> Edi Weitz <edi at agharta.de> writes:
>
>> If you really need it, you could loop through the string applying
>> SCAN until it matches with decreasing values for START, but that
>> could be quite inefficient, of course. An alternative would be to
>> work on (REVERSE TARGET) instead of TARGET, but you'll have to
>> think hard how your regular expression should look like in that
>> case - the semantics of things like "*" will certainly be
>> different.
>
> I was afaid you'd say that :). I guess I'll look closer into how
> emacs does it.

Of course, if you're really adventurous, you could look at the source
code of CREATE-SCANNER-AUX in CL-PPCRE and think about efficient
variants of ADVANCE-FN for searching backwards.  My guess (from
looking at the Emacs C code for two minutes) is that this is more or
less what Emacs is doing as well.