Subject:
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Re: Strip surplus white space with Perl
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Sun, 29 Oct 2000 21:25:03 GMT
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Viewed:
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141 times
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In lugnet.off-topic.geek, Christopher Lindsey writes:
> Christopher Lindsey wrote:
> > Ahh, but what happens if you have a carriage return followed by a
> > space? The second method eliminates the space and leaves the
> > carriage return, which isn't what he asked for.
Ahh, but that *is* what he asked for. Fredrik said, "If two consecutive
characters are <SPACE> and <RET>, for example, it doesn't matter to me
which one is preserved and which one is chopped off."
> [...]
> This should do it:
>
> $string =~ s/(\t\t+| +|\r\r+|\n\n+|\f\f+)/substr($&,1,1)/eg;
My goodness. I suppose you could do it that way, but why go through all that
trouble when all you want to do is this?--
$string =~ s/(\s)\1+/$1/g;
Or, if you want to enumerate whitespace characters explicitly (because \n
isn't guaranteed to map to \012 and \r isn't guaranteed to map to \015):
$string =~ s/([\009\040\015\012])\1+/$1/g;
> Yes, a /g will work here, David was right about that. I usually stick
> with a while loop because in some cases it's better (i.e. if you're
> using $` and don't want to recalculate things like length from the start
> of the string each time).
Could you give a concrete example? I'm curious -- I've always believed that
/g is faster (and clearer code) than using a while, even when there aren't
lots of matches. Doesn't
while ($string =~ s///) {}
have O(n^2) performance, where n is the number of hits in the string? Or are
you hiding some anchors in there?
--Todd
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Message has 2 Replies:
 | | Re: Strip surplus white space with Perl
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| (...) There are some days when I shouldn't touch a keyboard. I read and reread his initial posting and could have sworn that it said "It *does* matter to me which one..." I think you just went in and edited the message. ;) I guess it's one of those (...) (24 years ago, 29-Oct-00, to lugnet.off-topic.geek)
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Message is in Reply To:
| | Re: Strip surplus white space with Perl
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| (...) I hate replying to myself, but I realize that I pasted the wrong answer into my initial response now, and totally missed the boat on my response to David. Ooops. :) This should do it: $string =~ s/(\t\t+| +|\r\r+|\n\n+|\f\f+)...&,1,1)/eg; Yes, (...) (24 years ago, 29-Oct-00, to lugnet.off-topic.geek)
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