Re: Using map to create a hash/bag from an array

[GrandFather]

The idiomatic way to do that in Perl is @hash{qw(a b c)} = (1) x 3;:

use strict;
use warnings;
use Data::Dumper;

my %hash;
@hash{qw(a b c)} = (1) x 3;
print Dumper (\%hash);

Prints:

$VAR1 = {
          'c' => 1,
          'a' => 1,
          'b' => 1
        };

[bart]

Except, IMHO, the hash values are irrelevant. Codewise, it's easier to use undef as hash values: your

@hash{qw(a b c)} = (1) x 3;

then becomes

@hash{qw(a b c)} = ();

That's a lot shorter, isn't it? And no need to count items.

[GrandFather]

And faster too (making the obvious benchmark addition):

         Rate   set   map map++    GF  Bart
set    2288/s    --  -84%  -91%  -92%  -93%
map   14566/s  537%    --  -46%  -48%  -58%
map++ 26756/s 1070%   84%    --   -4%  -23%
GF    27881/s 1119%   91%    4%    --  -19%
Bart  34580/s 1412%  137%   29%   24%    --

See Re: Using map to create a hash/bag from an array for the original code