How can I cleanly turn a nested Perl hash into a non-nested one?
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by knorv
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Published on 2010-03-22T20:52:16Z
Indexed on
2010/03/23
17:33 UTC
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Assume a nested hash structure %old_hash
..
my %old_hash;
$old_hash{"foo"}{"bar"}{"zonk"} = "hello";
.. which we want to "flatten" (sorry if that's the wrong terminology!) to a non-nested hash using the sub &flatten(...)
so that ..
my %h = &flatten(\%old_hash);
die unless($h{"zonk"} eq "hello");
The following definition of &flatten(...)
does the trick:
sub flatten {
my $hashref = shift;
my %hash;
my %i = %{$hashref};
foreach my $ii (keys(%i)) {
my %j = %{$i{$ii}};
foreach my $jj (keys(%j)) {
my %k = %{$j{$jj}};
foreach my $kk (keys(%k)) {
my $value = $k{$kk};
$hash{$kk} = $value;
}
}
}
return %hash;
}
While the code given works it is not very readable or clean.
My question is two-fold:
- In what ways does the given code not correspond to modern Perl best practices? Be harsh! :-)
- How would you clean it up?
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