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Problem with HOA.

by tamaguchi (Pilgrim)
on Aug 28, 2006 at 07:03 UTC ( #569938=perlquestion: print w/ replies, xml ) Need Help??
tamaguchi has asked for the wisdom of the Perl Monks concerning the following question:

Suppose you have following data stucture:
my %hash=( 1=> [1.5, 2.1, 3.1], 2=> [1.2, 2.2, 3.2], 3=> [1.3, 2.3, 3.3], )
How would you do in the easiest way to get out an array consisting of the first ellement in each of the internal valuearrays sorted by the keys? I.e. $array[0]=1.5,  $array[1]=1.2 and $array[2]=1.3. Thank you fellow monk.

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Re: Problem with HOA.
by cog (Parson) on Aug 28, 2006 at 07:10 UTC
    my @array = map { $hash{$_}->[0] } sort { $a <=> $b } keys %hash;

    That's the first solution that comes to my mind. Try reading it backwards:

      1. Take the keys of the hash... (keys %hash)
      2. ...sort them numerically... (sort { $a <=> $b } ...)
      3. ...and get the first element of the array corresponding to each key in the hash... (map { $hash{$_}->[0] } ...)
Re: Problem with HOA.
by GrandFather (Cardinal) on Aug 28, 2006 at 07:13 UTC

    Update wrong answer. cog has it right.

    use strict; use warnings; my %hash=( 1=> [1.5, 2.1, 3.1], 2=> [1.2, 2.2, 3.2], 3=> [1.3, 2.3, 3.3], ); my @array = sort {$a<=> $b} map {@{$hash{$_}}} keys %hash; print "@array";

    Prints:

    1.2 1.3 1.5 2.1 2.2 2.3 3.1 3.2 3.3

    DWIM is Perl's answer to Gödel

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