TASdvlper has asked for the wisdom of the Perl Monks concerning the following question:

Hello all,

I have two arrays of equal sizes, is there a way I can use one array for the "keys" of a hash and the other array the "values" of a hash (assuming 1:1 mapping) ? 

@array1 = qq (foo, foo1, foo2, foo3, foo4, ...)
@array2 = qq (bar, bar1, bar2, bar3, bar4, ...).

[download]
and I want the hash to look like: 
$myhash{'foo'}  = 'bar';
$myhash{'foo1'} = 'bar1';
$myhash{'foo2'} = 'bar2';
$myhash{'foo3'} = 'bar3';
$myhash{'foo4'} = 'bar4';

[download]
Any help would be greatly appreciated.

Replies are listed 'Best First'.
Re: Populating a hash from array
by jeffa (Bishop) on Jan 05, 2004 at 21:36 UTC
    This is known as a hash slice: 
    my %hash;
@hash{@array1} = @array2;

    [download]
    The key is to declare the hash first, then apply the slice.

    jeffa

    L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
[reply]
[d/l]
      thanks ... I remember reading about hash slices but, until now, never had a need to use them.
[reply]
Re: Populating a hash from array
by duff (Parson) on Jan 05, 2004 at 21:36 UTC

    @hash{@keys} = @values;

    duff

[reply]
[d/l]
Re: Populating a hash from array
by Abigail-II (Bishop) on Jan 05, 2004 at 21:36 UTC 
    my %myhash;
   @myhash {@array1} = @array2;

    [download]

    Abigail

[reply]
[d/l]
Re: Populating a hash from array
by bart (Canon) on Jan 05, 2004 at 22:03 UTC 
    @array1 = qq (foo, foo1, foo2, foo3, foo4, ...)
@array2 = qq (bar, bar1, bar2, bar3, bar4, ...).

    [download]
    As a sidenote, you don't want qq, you want qw. And get rid of the commas. 
    @array1 = qw(foo foo1 foo2 foo3 foo4 ...);
@array2 = qw(bar bar1 bar2 bar3 bar4 ...);

    [download]
[reply]
[d/l]
[select]
      thanks ... probably just a typo on my part.
[reply]
        TASdvlper,
        In addition to what bart said, if your data really does look like this - there is probably a much better way to build your array (the lazy way). 
        my @array1 = map { 'foo' . $_ } 1 .. 99;

        [download]
        "Ok great, but I want the first element to just be 'foo' with no number" 
        my @array1 = map { $_ ? 'foo' . $_ : 'foo' } 0 .. 99;

        [download]
        Cheers - L~R
[reply]
[d/l]
[select]
Re: Populating a hash from array
by Roger (Parson) on Jan 05, 2004 at 22:36 UTC
    Hash slice is (usually) the way to go.

    You can also use the map function to build the hash, as illustrated by the following example:
    my %myhash = map { $array1[$_] => $array2[$_] } 0 .. $#array1;

    [download]

[reply]
[d/l]
Re: Populating a hash from array
by ryantate (Friar) on Jan 05, 2004 at 21:55 UTC

    I was just thinking about hash slices the other day, and wondering: what is the syntax for slicing a hash -reference-? I always end up doing things like

    ($hashref->{key1}, $hashref->{key2}) = @values;

    or

    {map {$keynames[$_]=>$values[$_]} 0 .. $#values};

    which seems much less elegant.

[reply]
[d/l]
[select]
      what is the syntax for slicing a hash -reference-?
      @{$href}{@keys}
[reply]
[d/l]
        If the reference is a simple scalar, you can just say @$href{@keys}. The curly braces around the reference are only necessary if the reference is a more complicated expression (e.g. @{gimme_href()}{@keys}).

        Same thing goes with using a slice or $# (last index) on an array reference: @$aref[@indices] and $#$aref or @{gimme_aref()}[@indices] and $#{gimme_aref()}.

        Of course, if the curlies make it more clear to you, by all means use them.

[reply]
[d/l]
[select]
[reply]
Re: Populating a hash from array
by Anonymous Monk on Jan 06, 2004 at 18:55 UTC 
    %myhash = map { $array1[$_] => $array2[$_] } ( 0 .. $#array1);

    [download]
[reply]
[d/l]

Back to Seekers of Perl Wisdom