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

by GrandFather (Sage)
on Dec 17, 2005 at 10:41 UTC ( #517462=note: print w/replies, xml ) Need Help??

in reply to Using map to create a hash/bag from an array

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);


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

DWIM is Perl's answer to Gödel

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Re^2: Using map to create a hash/bag from an array
by bart (Canon) on Dec 18, 2005 at 10:45 UTC
    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.

      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

      DWIM is Perl's answer to Gödel

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[ambrus]: So that, or if you really want something agnostic to the loop, then use curl multi. Its interface is quite reasonable (unless you use an old version),
[ambrus]: though it's very C-like (serious use of varargs so easy to pass the wrong type), and there are some minor problems (busy loop because it doesn't use the same timer as your event loop, so you have to artificially delay timer callbacks by a small amount).

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