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Re: s///e

by maverick (Curate)
on May 02, 2002 at 19:25 UTC ( #163644=note: print w/ replies, xml ) Need Help??


in reply to s///e
in thread How do I replace all characters in a string with X's except the last 4 character

Here's yer tuit...

use Benchmark; my $string = "1234567890"; timethese(-5, { 'Regexp' => sub { $string =~ s/(.*?)(....)$/("X" +x length($1)).$2/e; }, 'Regexp D&P' => sub { $string =~ s/.(?!.{0,3}$)/x/g; +}, 'Substring' => sub { $string = length substr($string +,0,-4). substr($string,-4) } });
Yields:
Benchmark: running Regexp, Regexp D&P, Substring, each for at least 5 +CPU seconds... Regexp: 6 wallclock secs ( 5.38 usr + 0.00 sys = 5.38 CPU) @ 17 +3245.35/s (n=932060) Regexp D&P: 6 wallclock secs ( 5.30 usr + 0.00 sys = 5.30 CPU) @ 20 +0480.57/s (n=1062547) Substring: 7 wallclock secs ( 5.45 usr + 0.00 sys = 5.45 CPU) @ 10 +04355.05/s (n=5473735)
This is on a 2 GHz Pentium 4. Let's say we increase $string to 1000 characters...
Benchmark: running Regexp, Regexp D&P, Substring, each for at least 5 CPU seconds...
    Regexp:  6 wallclock secs ( 5.29 usr +  0.00 sys =  5.29 CPU) @ 4194.33/s (n=22188)
Regexp D&P:  5 wallclock secs ( 5.26 usr +  0.00 sys =  5.26 CPU) @ 2068.25/s (n=10879)
 Substring:  7 wallclock secs ( 5.26 usr +  0.00 sys =  5.26 CPU) @ 1022051.33/s (n=5375990)
Update: Added Dog_and_Pony's solution...
Update 2:Fixed stupid bug in Substring code. , and . do different things...
Update 3:abstracts spotted that my substring function has a cut and paste error (sheesh). jsprat's benchmark is accurate. The four arg substring seems to be the fastest.

/\/\averick
OmG! They killed tilly! You *bleep*!!


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