RE: (tye)Re: Regular expression to match an A=B type string needs help in storing matched parts of string

Why is that, tye? There's no reason to make the + non-greedy. There's no way for [^=] to match an =. Here's a benchmark:

#!/usr/bin/perl
use Benchmark 'timethese';
$short = "abcdefg";
$long = $short x 100;
timethese(-5, {
  japhyS => q{ "$short=123" =~ /[^=]+=/ },
  tyeS => q{ "$short=123" =~ /[^=]+?=/ },
  japhyL => q{ "$long=123" =~ /[^=]+=/ },
  tyeL => q{ "$long=123" =~ /[^=]+?=/ },
});
__END__
Benchmark: running japhyL, japhyS, tyeL, tyeS,
  each for at least 5 CPU seconds...
 japhyL:  5803.60/s (n=29018)
   tyeL:  1785.83/s (n=8947)
 japhyS:  30179.50/s (n=157537)
   tyeS:  26449.44/s (n=141240)
[download]

It gets worse for longer strings.

$_="goto+F.print+chop;\n=yhpaj";F1:eval

Comment on RE: (tye)Re: Regular expression to match an A=B type string needs help in storing matched parts of string Download Code

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RE: RE: (tye)Re: Regular expression to match an A=B type string needs help in storing matched parts of string by tye (Sage) on Sep 21, 2000 at 22:12 UTC
Well, I was thinking of the string after the "=" being long, but the greedy version still wins. Perhaps the regex works from the back even when non-greedy? My (incorrect, apparently) thinking was that `/[^=]+=/` will have to check the whole string to make sure there isn't a second "=" later on while `/[^=]+?=/` could just stop at the first "=" (provided the rest of the regex matched). I'd be interested in any insights on this. [ Didn't I make this exact same mental error before... I'll have to go check and then double check the read-only tab on my brain ] - tye (but my friends call me "Tye")	[reply] [d/l] [select]
RE: RE: RE: (tye)Re: Regular expression to match an A=B type string needs help in storing matched parts of string by japhy (Canon) on Sep 21, 2000 at 22:28 UTC
In the regex `/[^=]+=/`, the `[^=]` part matches NON-= characters. The `=` then matches an = sign after the non-= characters. That's basically all I can think to say... `$_="goto+F.print+chop;\n=yhpaj";F1:eval`	[reply]