Re^2: specific array in hash of arrays

moritz explained, so what follows is a solution. Basically, comparing a single value against an array makes so sense. By using grep, the value can be compared against every element of the array.

#!/usr/bin/perl

use strict;
use warnings;

my %hoa = (
   arraya => [qw( dd1 dd2 dd3 dd4 )],
   arrayb => [qw( gg1 gg2 gg3 gg4 )],
   arrayc => [qw( cc1 cc2 cc3 cc4 )],
);

chomp( my $array_name = <STDIN> );   # e.g. arraya 
chomp( my $to_find    = <STDIN> );   # e.g. dd2

if (  exists( $hoa{$array_name} )
   && grep { $_ eq $to_find } @{$hoa{$array_name}}
) {
   print( @{$hoa{$array_name}}, "\n" );
}
[download]

Comment on Re^2: specific array in hash of arrays Select or Download Code

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Re^3: specific array in hash of arrays by gone2015 (Deacon) on Oct 09, 2008 at 13:54 UTC
Though looking up a hash will often be better than doing a linear search along a list. For example: `#!/usr/bin/perl use strict; use warnings; my %hoh = ( flasha => { dd1 => 1, dd2 => 2, dd3 => 3, dd4 => 4 }, flashb => { gg1 => 1, gg2 => 2, gg3 => 3, gg4 => 4 }, flashc => { cc1 => 1, cc2 => 2, cc3 => 3, cc4 => 4 }, ); for ([qw(flasha dd4)], [qw(glashz gg2)], [qw(flashc zz)], [qw(flashc c +c1)]) { my ($array_name, $to_find) = @$_ ; if (exists $hoh{$array_name}->{$to_find}) { print( "$array_name contains $to_find\n" ); } }` [download] noting that `exists` stops looking, without complaint, if `$hoh{$array_name}` doesn't exist. If the list is a trivial length, then `List::Util::first` at least stops looking when it gets a match. I don't know what you need to do having discovered the match... the above allows you to map "array name" and "to_find" to anything you like -- the numbers above are for illustration, only ! If you're only interested in existence, then `flasha => { map { ($_, undef) } qw(dd1 dd2 dd3 dd4) },` [download] will serve.	[reply] [d/l] [select]
Re^4: specific array in hash of arrays by ikegami (Patriarch) on Oct 09, 2008 at 14:11 UTC
`if (exists $hoh{$array_name}->{$to_find}) {` [download] should normally be `if ( exists( $hoh{$array_name} ) && exists( $hoh{$array_name}->{$to_find} ) ) {` [download] to prevent autovivification of entries into `%hoh`. That might not matter here, though.	[reply] [d/l] [select]
Re^5: specific array in hash of arrays by gone2015 (Deacon) on Oct 09, 2008 at 15:01 UTC
Rats... "autovivication" :-( Just when I thought I was getting to grips with Perl magic, another piece bites me in the backside... "autovivifying" an rvalue ? ...of course, silly me !	[reply]
Re^6: specific array in hash of arrays by ikegami (Patriarch) on Oct 09, 2008 at 15:21 UTC
Re^3: specific array in hash of arrays by kwn (Novice) on Oct 09, 2008 at 11:23 UTC
I think you answered my question as I was writing it! Awesome thanks.	[reply]