if we're talking about optimization and the question was really how to
CAPTURE the characters after the last /
there is really NO need for a s/// and a simple m// would do
which i imagine will also be quite a bit faster
regards,
jos
----- Original Message -----
From: "Gary Hawkins" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; "David" <[EMAIL PROTECTED]>
Sent: Sunday, January 06, 2002 11:48 PM
Subject: RegEx speed (was: Using regexp to get a substring)
> That'll work, but on a finer point, if you need to be thinking about
> optimization at the moment:
>
> ($substring1 = $string) =~ s/.*\\(.*)/$1/;
>
> ....is about 4 times slower than:
>
> ($substring2 = $string) =~ s/.*\\//;
>
> ....because the second one doesn't have to store the matched value inside
the
> parens in $1.
>
> In test below:
> substring1 code took: 20 wallclock secs (20.05 usr + 0.00 sys = 20.05
CPU)
> substring2 code took: 5 wallclock secs ( 5.15 usr + 0.00 sys = 5.15
CPU)
>
> So it can be best to use $1 thru $9 only when necessary if speed matters.
>
> Gary
>
> ======
>
> Notes:
>
> In this test script we do the substitution a million times for each method
and
> then print the benchmark results. You can tailor this script to check the
> comparison on any two or more different ways of doing something.
>
> #!perl.exe
>
> use Benchmark;
>
> $string ='C:\PerlScripts\TestSamples\StringTest.pl';
>
> # substring1 method
> $i = 0;
> $t0 = new Benchmark;
> while ($i < 1000000) {
> ($substring1 = $string) =~ s/.*\\(.*)/$1/;
> $i++;
> }
> $t1 = new Benchmark;
> $td = timediff($t1, $t0);
> print "substring1 code took: ", timestr($td), "\n\n";
>
> # substring2 method
> $i = 0;
> $t0 = new Benchmark;
> while ($i < 1000000) {
> ($substring2 = $string) =~ s/.*\\//;
> $i++;
> }
> $t1 = new Benchmark;
> $td = timediff($t1, $t0);
> print "substring2 code took: ", timestr($td), "\n\n";
>
> __END__
>
> Printed result:
>
> substring1 code took: 20 wallclock secs (20.05 usr + 0.00 sys = 20.05
CPU)
>
> substring2 code took: 5 wallclock secs ( 5.15 usr + 0.00 sys = 5.15
CPU)
>
>
> > -----Original Message-----
> > From: Shawn [mailto:[EMAIL PROTECTED]]
> > Sent: Sunday, January 06, 2002 1:03 PM
> > To: [EMAIL PROTECTED]; David
> > Subject: Re: Using regexp to get a substring
> >
> >
> > "David" <[EMAIL PROTECTED]> wrote in message
> > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > > Hello All,
> > >
> > > I am beginner and need some helps. Thanks a lot!
> > >
> > > The question is, if I have a string, for example
> > > "C:\PerlScripts\TestSamples\StringTest.pl", how do I use regexp to
parse
> > > this string and get substring after the last backslash
("StringTest.pl").
> >
> > Hey David,
> > This should work for you:
> >
> > use strict;
> > my $String='C:\PerlScripts\TestSamples\StringTest.pl';
> > (my $substring =$string) =~s/.*\\(.*)/$1/;
>
>
> --
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
>
>
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
