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Re: Merging hashes

by kabel (Chaplain)
on Sep 10, 2002 at 12:07 UTC ( #196636=note: print w/replies, xml ) Need Help??

in reply to Merging hashes

in fact those need to be references due to list flattening. your %hash1 is not built as you want (same for %hash2). you can see this by just printing out your data structures and try to guess what happens:
use strict; use Data::Dumper; my %hash1; # fill %hash1 here print Dumper \%hash1;

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Re: Re: Merging hashes
by hotshot (Prior) on Sep 10, 2002 at 12:19 UTC
    Got it, in fact I use references (it's my question that wasn't clear enough), the thing is that I always stay with one value for the same keys, if I'll take my example from the question, then I get only one brown entry. The references always clober each other and not added, I didn't seem to solve that yet.

      Thats what hashes do. map a unique key to a unique values. But you can make that value an array ref and store your multiple values.

      It also looks like you want to apply it recursively. May I ask what you are trying to do?


      "To be civilized is to deny one's nature."
      Here's enough rope to hang yourself with.
      Merges N hashes arbitrarily deep. Making it merge arrays as well is left as an exercise for the reader.
      Dies on circular references. Not heavily tested.
      #!/usr/bin/perl use warnings; use strict; use Data::Dumper; BEGIN { my %SeenMerged = (); sub mergehashes{ # Dies on circular references my @hashrefs = @_; die "Passed a non hashref" if grep { ref $_ ne 'HASH' } @h +ashrefs; my %merged = (); my @seen = grep { ref $_ eq 'HASH' } @SeenMerged{@hashref +s}; # Break circular links.. if (@seen){ die "contains a circular reference! bailing..."; } @SeenMerged{@hashrefs} = @hashrefs; foreach my $h (@hashrefs){ while (my ($k,$v) = each %$h ){ push @{$merged{$k}}, $v; } } while (my ($k,$v) = each %merged){ my @hashes = grep { ref $_ eq 'HASH' } @$v; $merged{$k} = $v->[0] if (@$v == 1 && !ref $v->[0]); + $merged{$k} = mergehashes(@hashes) if @hashes; } delete @SeenMerged{@hashrefs}; return \%merged; } } my %hash1 = ( red => 1, brown => { green => 1, blue => { yellow => 1, }, black => 1, }, gray => 1, ); my %hash2 = ( white => 1, brown => { purple => 1, }, ); my $merged = mergehashes(\%hash1, \%hash2) ;#or die "Couldn't merge!"; print Dumper($merged);
        but if I don't work with references, and do something like:
        $hash{red}{blue} = 1; $hash{red}{green} = 1;
        I get;
        %hash = ( red => ( blue => 1, green => 1, ), );
        I want that to happen with references too.


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