> >
m{https?://[^/\s]+?(?<!\.com)(?<!\.net)(?<!\.org)(?<!\.gov)(?<!\.us)(?<!\.ed
u)(?<!\.mil)(\/\[^\s])?}
> >
> >
> One of the amazing things about posting to lists is that shortly after
> posting I usually find the answer to the question. Well, I've now
> learned something about negative look-ahead assertions that I did not
Actually that is a negative lookBEHIND assertion that they are using.
Negative lookAHEAD is (?!, not (?<!.
What this test is saying, in more or less english is: Match 'http', possibly
followed by 's', and then followed by '//:'. Then match everything up to a
/ or space, but don't be greedy about it. (which means, stop on the FIRST /
or space you find, not the last one.) Now that you are pointing at a / or
space, are the preceeding 4 characters not .com, and not .net, etc.
Then we get to the last part, which I suspect you added, since the coding
style is different, and it does some things it odd things. In fact, I'm
not at all sure exactly what the intent was here. I think perhaps it was
trying to look for a / optionally followed by a space after the url. But we
already know that there is a / or space here from the original non-greedy
match.
In any case, if that was the intent, it should have been coded as
"(?:/[^\s])?". The ?: after the ( says that you are only using the parends
as grouping, and not as a capturing group. This is MUCH faster, according
to the Perl pundits. You don't need a backslash in front of the slash in
this case, because the overall delimiter characters are {} instead of the
more common //. And you certainly don't want a backslash in front of the
[ character that is part of the character grouping, unless you wanted to
compare a literal [ character. In that case you would also need a backslash
in front of the ] character.
(I suspect that the appropriate match here would be simply "[/\s]" to match
the slash or space we know is here. Or more simply, just a dot. We don't
care what it matches, and we already have a pretty good idea of what it will
match.)
Loren
