On Nov 24, 7:06 pm, jwkr...@shaw.ca (John W. Krahn) wrote:
> ...
> > 1. before the a
> > 2. between the a and b
> > 3. before the b
> > 4. after the b
>
> > The problem is that the third one should not be there.
>
> Yes it should. Perhaps you are confused because pos() reports the
> current position *after* the match has occured? A zero width match has
> the same position at the beginning and end however the 'XXX' string has
> a different position at the beginning and end. Try using $-[0] for the
> beginning of the match and $+[0] for the end of the match.
>
> $ perl -le '$_="aXXXb"; print "one word is $1 at $-[0] to $+[0]" while
> /(X*)/g;'
> one word is at 0 to 0
> one word is XXX at 1 to 4
> one word is at 4 to 4
> one word is at 5 to 5
>
The match, pre-match, post-match captures can be helpful at times
IMO to see what's going on:
$_="aXXXb";
print "one word is ", ( $& eq ''" ? "empty " : " $& "),
"pre:$` post:$' " while /(X*)/gp;
Or, using 5.10.0 to avoid the $&, $`, $' penalty:
print "one word is ",
( ${^MATCH} eq '"" ? "empty " : "${^MATCH} "),
"pre:${^PREMATCH} post:${^POSTMATCH}"
while /(X*)/gp;
one word is empty pre: post:aXXXb
one word is XXX pre:a post:b
one word is empty pre:aXXX post:b
one word is empty pre:aXXXb post:
--
Charles DeRykus
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