PERL Beginners - array against array regexp

Author

array against array regexp

Ing. Branislav Gerzo

2005-06-05, 3:56 pm

Hi all,

let's we have:

use strict;
use warnings;

my @input = qw{ one two twentythree four };
my @filter = qw { one three five ten twenty };

my @filtered = ();
for my $in (@input) {
for my $filter (@filter) {
push @filtered, $in if $in =~ /$filter$/i;
}
}

I'd like to get new @filtered array, where will be only values
from @input against @filter.

but my snippet is 6 lines, I think it should be written in 1 line, with
using grep and map, but I'm not sure how.

Also we can say, input is always smaller than @filter (for
optimalization)

Anyone ? :)

Randal L. Schwartz

2005-06-05, 3:56 pm

>>>>> "Ing" == Ing Branislav Gerzo <konfera@2ge.us> writes:

Ing> Hi all,
Ing> let's we have:

Ing> use strict;
Ing> use warnings;

Ing> my @input = qw{ one two twentythree four };
Ing> my @filter = qw { one three five ten twenty };

Ing> my @filtered = ();
Ing> for my $in (@input) {
Ing> for my $filter (@filter) {
Ing> push @filtered, $in if $in =~ /$filter$/i;
Ing> }
Ing> }

Ing> I'd like to get new @filtered array, where will be only values
Ing> from @input against @filter.

Ing> but my snippet is 6 lines, I think it should be written in 1 line, with
Ing> using grep and map, but I'm not sure how.

## first, precompile all the regex for speed:
@filter = map qr/$_$/i, @filter;
## now grep the wanteds
my @filtered = grep {
my $wanted = 0;
my $input = $_;
$wanted ||= $input =~ /$_/ for @filter;
$wanted;
} @input;

Note the use of ||= for short-circuiting the tests once a good filter
is found. You can't use "return 1", because a grep/map block is not a
subroutine.

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Ing. Branislav Gerzo

2005-06-06, 8:55 am

Randal L. Schwartz [RLS], on , , 2005 at 05:47 (-0700) wrote about :

RLS> $wanted ||= $input =~ /$_/ for @filter;
RLS> $wanted;
RLS> } @input;

RLS> Note the use of ||= for short-circuiting the tests once a good filter
RLS> is found. You can't use "return 1", because a grep/map block is not a
RLS> subroutine.

very nice example, thanks a lot.

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