Sébastien Aperghis-Tramoni wrote:
> Q: Why do you use /[Tt]/ instead of /t/i? It's so ugly!
>
> A: Simple - the case-insensitive match switch is very
> inefficient. According to "Mastering Regular Expressions"
> from O'Reilly Press, /[Tt]/ is faster and more space
> efficient than /t/i - by as much as double against long
> strings. //i essentially does a lc() on the string and
> keeps a temporary copy in memory.
>
> When this changes, and it is in the 5.6 development series,
> I will gladly use //i. Believe me, I realize [Tt] is hideously
> ugly.
Looks like it was painfully true for 5.5...
$ time perl5.5.5 -wle '$foo = "x" x 10000; $foo .= "T"; $foo =~ /[Tt]/ for
1..100000'
real 0m4.882s
user 0m4.761s
sys 0m0.026s
$ time perl5.5.5 -wle '$foo = "x" x 10000; $foo .= "T"; $foo =~ /t/i for
1..100000'
real 0m40.656s
user 0m39.587s
sys 0m0.149s
And the reverse is now true in this highly inaccurate test...
$ time perl5.8.8 -wle '$foo = "x" x 10000; $foo .= "T"; $foo =~ /[Tt]/ for
1..100000'
real 0m5.732s
user 0m5.565s
sys 0m0.027s
$ time perl5.8.8 -wle '$foo = "x" x 10000; $foo .= "T"; $foo =~ /t/i for
1..100000'
real 0m2.589s
user 0m2.544s
sys 0m0.015s
--
<Schwern> What we learned was if you get confused, grab someone and swing
them around a few times
-- Life's lessons from square dancing
