38 lines
746 B
Plaintext
38 lines
746 B
Plaintext
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###
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### powerset_recurse4
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###
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## Chapter 5 section 4.1.1
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sub powerset_recurse ($) {
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my ( $set ) = @_;
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my $null = { };
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my $powerset = { $null, $null };
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while (my ($key, $value) = each %$set) {
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my @newitems;
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while (my ($powerkey, $powervalue) = each %$powerset) {
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my %subset = ( );
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# Copy the old set to the subset.
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@subset{keys %{ $powerset->{$powerkey} } } =
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values %{ $powerset->{$powervalue} };
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# Add the new member to the subset.
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$subset{$key} = $value;
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# Prepare to add the new subset to the powerset.
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push @newitems, \%subset;
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}
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$powerset->{ $_ } = $_ for @newitems;
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}
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return $powerset;
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}
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