CODEWITHSUNDEEP
perlhash
steelcityamir
steelcityamir

Reputation: 1218

Determine if hash1 data exists in hash2 in Perl

Say I have 2 hashes:

my %hash1 = ('file1' => 123, 'file3' => 400);
my %hash2 = ('file1' => 123, 'file2' => 300, 'file3' => 400);

What's the best way to determine if the key/value pairs in hash1 do not exist in hash2?

Upvotes: 0

Views: 187

Answers (2)

Axeman
Axeman

Reputation: 29854

I like to use the new pairwise features of List::Util. (Well, actually I've been using my own version of them for a long time, even before List::Pairwise.)

use strict;
use warnings;

no warnings 'experimental';
use List::Util qw<pairgrep pairmap>;

my %hash1 = ('file1' => 123, 'file3' => 402);
my %hash2 = ('file1' => 123, 'file2' => 300, 'file3' => 400);

my @comp 
    = pairmap  { $a } 
      pairgrep { not ( exists $hash2{ $a } and $hash2{ $a } ~~ $b ) }
      %hash1
    ;

Note that $hash1{file3} was changed to 402, to make a solution set.

Upvotes: 1

fugu
fugu

Reputation: 6578

my %hash1 = ('file1' => 123, 'file3' => 400);
my %hash2 = ('file1' => 123, 'file2' => 300, 'file3' => 400);

foreach my $key (keys %hash1){
    print "$key\t$hash1{$key}\n" if !exists $hash2{$key};
    print "$hash1{$key}\n" if $hash1{$key} != $hash2{$key};
}

Which outputs nothing, as all the keys that exist in %hash1 also exist in %hash2, and all the values for each key are the same

Upvotes: 3

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