Re^2: my 'if' condition doesn't work, why?

The core List::Util first function is like grep but returns the first element found:

use List::Util qw(first);
for my $n (0 .. 267) {
    print "$n\n" if first {$n == $_} 40, 47, 76;
}
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and so should be faster for very large lists.

Comment on Re^2: my 'if' condition doesn't work, why? Select or Download Code

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Re^3: my 'if' condition doesn't work, why? by AnomalousMonk (Archbishop) on Nov 12, 2014 at 12:10 UTC
A problem with List::Util`::first()` as used in the example above is that it actually returns the first element from the list that satisfies the condition. If this value happens to be false, the `if`-statement modifier will not satisfied, and the dependent statement will not be executed. Neither `any` nor `grep` nor a hash lookup have this problem. `c:\@Work\Perl>perl -wMstrict -le "use List::Util qw(first); ;; for my $n (0 .. 267) { printf qq{$n } if first {$n == $_} 40, 0, 47, 76; } print qq{\n----------}; ;; ;; for my $n (0 .. 267) { printf qq{$n } if grep { $n == $_ } 40, 0, 47, 76; } " 40 47 76 ---------- 0 40 47 76` [download]	[reply] [d/l] [select]
Re^3: my 'if' condition doesn't work, why? by GrandFather (Saint) on Nov 12, 2014 at 08:03 UTC
On average 50% faster which often doesn't help much. However if speed is an issue and the search needs to be done multiple times with the same data, using a hash lookup is a much better solution. Perl is the programming world's equivalent of English	[reply]