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Re: Regular Expression

by Enlil (Parson)
on Feb 09, 2005 at 19:34 UTC ( [id://429485]=note: print w/replies, xml ) Need Help??


in reply to Regular Expression

You can do this a variety of ways, but here are three: 
$string =~ m/abc.*xyz|xyz.*abc/i
$string =~ m/(?=.*abc)(?=.*xyz)/i;
$string =~ /abc/i and $string =~ /xyz/i

[download]

The ampersands inside the regular expression will be matched as ampersands and not used as logical operators.

-enlil

Replies are listed 'Best First'.
Re^2: Regular Expression
by nobull (Friar) on Feb 09, 2005 at 20:14 UTC 
    $string =~ m/(?=.*abc)(?=.*xyz)/i;

    [download]

    That unanchored pattern is pathologically inficient. If the string does not match it will try and fail at every character position. Even with a relatively short strings this has a considerable effect. 

    use Benchmark;
my $string = 'x' x 100;
timethese 1_000_000 => {
    unanchored => sub { $string =~ /(?=.*abc)(?=.*xyz)/i },
    anchored => sub { $string =~ /^(?=.*abc)(?=.*xyz)/i },
};

    [download]

    Benchmark: timing 1000000 iterations of anchored, unanchored...
    anchored: 1 wallclock secs ( 1.30 usr + 0.00 sys = 1.30 CPU) @ 768049.16/s (n=1000000)
    unanchored: 70 wallclock secs (70.12 usr + 0.00 sys = 70.12 CPU) @ 14261.06/s (n=1000000)

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