Perl Best Practices [Electronic resources] نسخه متنی

6.11. List Selections

Use grep and first instead of for when searching for values in a list .

The same principles apply when you want to refine a list by removing unwanted elements. Instead of a for loop:

# Identify candidates who are unfit for the cut-and-thrust of politics...
my @disqualified_candidates;
for my $name (@candidates) {
if (cannot_tell_a_lie($name)) {
push @disqualified_candidates, $name;
}
}

just use a grep:

# Identify candidates who are unfit for the cut-and-thrust of politics...

my @disqualified_candidates
= grep {cannot_tell_a_lie($_)} @candidates; 

Likewise, don't use a for when you're searching a list for a particular element:

# Victimize someone at random...
my $scapegoat = $disqualified_candidates[rand @disqualified_candidates];
# Unless there's a juicier story...
SEARCH:
for my $name (@disqualified_candidates) {
if (chopped_down_cherry_tree($name)) {
$scapegoat = $name;
last SEARCH;
}
}
# Publish and be-damn...
print {$headline} "Disgraced $scapegoat Disqualified From Election!!!\n";

Using the first function often results in code that is both more comprehensible and more efficient:

use List::Util qw( first );
# Find a juicy story...

my $scapegoat
= first { chopped_down_cherry_tree($_) }  @disqualified_candidates;
# Otherwise victimize someone at random...

if (!defined $scapegoat) {
$scapegoat = $disqualified_candidates[rand @disqualified_candidates];
}
# Publish and be-damn...

print {$headline} "Disgraced $scapegoat Disqualified From Election!!!\n";