Accidentally responded to originator, not list:
----- Forwarded message from [EMAIL PROTECTED] -----
On 14 Feb 02 at 10:25:13PM, Daniel R. Allen wrote:
> Thanks to all of the people who came up with answers. Ultimately the one
> I'm happiest with was the one Japhy emailed me, which shows that it can
> indeed be done in a regex.
Well, I think that's stretching it a bit. It's doing it with a "while"
loop that uses a regex among other operations.
Mind you, you can't really do much with just a regex; you generally
need m//xyz or s///xyz or split, at least, and often control
structures to provide repeated matching. People often ask "can you
give me a regex to do <blah>", when they mean "can you give me a
substitution statement to do <blah>" or more cynically, "I don't know
much about Perl, but I've heard Perl regexes can do everything...".
--
DRA previously:
> As I understand, perl uses the Boyer-Moore algorithm in the regex
> engine, so should it be possible to backtrack to the longest common
> string using a RE? Even if you don't know the text of the match
> beforehand?
I'm not sure what this has to do with B-M...I thought that was simply
an efficient algorithm for matching a specific substring. Backtracking
is a property of the matching engine.
None of the solutions are specifically using B-M to achieve the effect
you were after; but some use external code to work around the
limitations of the regex engine, one of which, it could be argued I
suppose, being that the regex engine can only match against a single
string...
---
I was curious to see what Japhy would do to join the strings (to allow
the regex engine to attack both together). I ended up shying away from
joining them, partly to avoid false matches (Japhy has ruled them out
by disallowing NULs), and partly because I thought it was simpler to
just do a plain string match using index() on the second string (which
I seem to remember reading uses B-M in its implementation...).
> And it even works in perl 5.005.
That's the shame about experimental features ("(?{})", which I used to
gain access to all the substrings to avoid the while loop, did not
work as well in earlier versions).
Regards,
Ian
----- End forwarded message -----
