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Re: Heisenberg Uncertainty Hash

by Roy Johnson (Monsignor)
on Apr 27, 2005 at 04:30 UTC ( #451848=note: print w/replies, xml ) Need Help??

in reply to Heisenberg Uncertainty Hash

Here's a demo of a sub you might find useful. It descends the hash chain checking existence at each level. It returns [a reference to, to ensure logical truth] the value if everything exists.
#!perl use warnings; use strict; sub safe_exists { my ($href, @list_of_descent) = @_; use List::Util 'first'; if (first { not (exists $href->{$_} and $href=$href->{$_}) } @list_of_descent) { return (); } else { return \$href; } } my %hash = ('a' => { 'value' => 1, 'foo' => 'bar', }, 'b' => { 'value' => 2, 'foo' => 'bar', }, 'c' => { 'value' => 3, 'foo' => 'bar', }, ); for (qw(a b c d)) { if (my $href = safe_exists(\%hash, $_, 'value')) { print "$_ value is $$href\n"; } else { print "Key $_ doesn't exist. Valid keys are: "; print join (", ", keys %hash), "\n"; } }

Caution: Contents may have been coded under pressure.

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[atcroft]: Lady_Aleena: By the way, I did look up another module (Tk), to see how it referred to other modules, and it used the L<module_name> POD linking, whereas the one I ran into today had hard-coded l<text|url> links.
[atcroft]: Sorry... L>text|url< links.
[atcroft]: Grrr.... L<text|url> links. .oO(Come on, brain, fingers, get it right this time.)

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