NAME

Hash::Subset - Produce subset of a hash

VERSION

This document describes version 0.002 of Hash::Subset (from Perl distribution Hash-Subset), released on 2019-07-10.

SYNOPSIS

 use Hash::Subset qw(hash_subset hashref_subset);

 # using keys specified in an array
 my %subset = hash_subset   ({a=>1, b=>2, c=>3}, ['b','c','d']); # => (b=>2, c=>3)
 my $subset = hashref_subset({a=>1, b=>2, c=>3}, ['b','c','d']); # => {b=>2, c=>3}

 # using keys specified in another hash
 my %subset = hash_subset   ({a=>1, b=>2, c=>3}, {b=>20, c=>30, d=>40}); # => (b=>2, c=>3)
 my $subset = hashref_subset({a=>1, b=>2, c=>3}, {b=>20, c=>30, d=>40}); # => {b=>2, c=>3}

DESCRIPTION

FUNCTIONS

None exported by default.

hash_subset

Usage:

 my %subset  = hash_subset   (\%hash, \@keys);
 my $subset  = hashref_subset(\%hash, \@keys);
 my %subset  = hash_subset   (\%hash, \%another_hash);
 my $subset  = hashref_subset(\%hash, \%another_hash);

Produce subset of %hash, returning the subset hash (or hashref, in the case of hashref_subset function).

Perl lets you produce a hashref using the slice notation:

 my %subset = %hash{"b","c","d"};

The difference with this routine is: 1) hash slice is only available since perl 5.20 (in previous versions, only array slices is available); 2) when the key does not exist in the array, perl will create it for you with undef as the value, so:

 my %hash   = (a=>1, b=>2, c=>3);
 my %subset = %hash{"b","c","d"}; # => (b=>2, c=>3, d=>undef)

So basically hash_subset is equivalent to:

 my %subset = %hash{grep {exists $hash{$_}} "b","c","d"}; # => (b=>2, c=>3, d=>undef)

and available for perl earlier than 5.20.

hashref_subset

See "hash_subset".

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Hash-Subset.

SOURCE

Source repository is at https://github.com/perlancar/perl-Hash-Subset.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Hash-Subset

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

SEE ALSO

Some other hash utilities: Hash::MostUtils

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2019 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.