Re: Finding a random position within a long string (Activeperl Build 822)

Seems straight forward enough...

my $string = 'ABC' x 1_000_000;
$string =~ s/(.)/( rand 10 < 1 ) ? '?' : $1/eg;

print $string;
[download]

I get: ABCABC?BC?BCABCABCABCA?CABCABCABCABCA?CABCABCABCABCAB?ABCABCABCABCABCABCABCABCA...

It's easy enough that I wonder if I'm misunderstanding your question.

Update: The full output has 298993 question marks and 2701007 other characters, but of course that varies with every execution.

Comment on Re: Finding a random position within a long string (Activeperl Build 822) Select or Download Code

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Re^2: Finding a random position within a long string (Activeperl Build 822) by lodin (Hermit) on Oct 12, 2007 at 23:57 UTC
You have a really nice Perlish solution. It's unnecessary to replace most of the string with itself though, if you can stand using an experimental assertion. The substitution would then look like this: `s/(?(?{rand() >= 0.1})(?!))./?/g` [download] Here's a benchmark comparing the two versions. use strict; use Benchmark qw(cmpthese timethese); my $str = '?' x 100_000; cmpthese(timethese(-10, { assertion => sub { $str =~ s/(?(?{rand() >= 0.1})(?!))./?/g; }, eval => sub { $str =~ s/(.)/rand() < 0.1 ? '?' : $1/eg; }, })); __END__ Benchmark: running assertion, eval for at least 10 CPU seconds... assertion: 11 wallclock secs (10.09 usr + 0.01 sys = 10.10 CPU) @ 8 +.51/s (n=86) eval: 11 wallclock secs (10.02 usr + 0.02 sys = 10.04 CPU) @ 3 +.09/s (n=31) Rate eval assertion eval 3.09/s -- -64% assertion 8.51/s 176% -- [download] lodin	[reply] [d/l] [select]
Re^2: Finding a random position within a long string (Activeperl Build 822) by mwah (Hermit) on Oct 12, 2007 at 21:40 UTC
Your solution: `$string =~ s/(.)/( rand 10 < 1 ) ? '?' : $1/eg;` [download] is very nice. This one does really work (in Win32/Activeperl). Thanks & Regards mwa	[reply] [d/l]