Re: 'grouping' substrings?

[murugu]

in reply to 'grouping' substrings?

I have come up with this. I dont know whether using $& is effecient or not.

use strict;
use warnings;
my $seq="IIIIIMMMMMMMMMMMOOOOOOOOOOOOOOOOMMMMMMMMMMMMMIIIIIMMMMMMMMMOO
+OOO
+OOOOOOOOOMMMMMMMMMMMMMIIIMMMMMMMMMMMOOOOOOOOOOOOOOOMMMMMMMMMMMIIIIIIM
+MMMMMMMMMMMMOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMIIIMMMMMMMMMOOOOOOOOOOOOOOO
+OOOOOOOOOOOOMMMMMMMIIIIMMMMMMMMMMMOOOOOOOOOOOOOOOOOOOOOMMMMMMMIIIMMMM
+MMMMMOOOOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMIIIMMMMMMMMMMMOOOOOOOOOOOOOOOO
+OMMMMMMMMI";
while ($seq=~/(M+)/g)  {
    my $l = pos($seq);
    print $l-length($&)+1," to ",$l,$/;
}

[revdiablo]

I dont know whether using $& is effecient or not.

Using $& is not efficient, and usually to be avoided. See the entry in perlvar for details.

Update: perhaps I was a bit imprecise. I'd say something that "imposes a considerable performance penalty on all regular expression matches" is inefficient, but I guess it depends on what type of inefficiency we're talking about.

[ikegami]

That's not exactly true. $& is only inefficient if you have another regexp in your program which doesn't capture.

However, it's use is discouraged, since captures can perform the same task without the "effect at a distance" of $&.

In this case, just replace $& with $1, and you're set.