How do I convert entire hash to lowercase?

CharlesClarkson has asked for the wisdom of the Perl Monks concerning the following question:

I am attepting to pass an optional anonymous hash as the first argument to a function. I allow any case for the keys and values. I then convert the hash in the hash reference to all lowercase. I have isolated the method I am using to this small script. My question is: Is there a way to convert the keys and values of a hash to all lowercase without using a temporary hash? (I realize this will change the original hash.)

#!/usr/bin/perl
use strict;
use diagnostics;
use Data::Dumper;

my $hash_ref = {    Extension   => '.txt',
                    Content     => 'text',
                    Directory   => 'c:/'    };

print Dumper $hash_ref;

my %lc_hash;
$lc_hash{lc $_[0]} = lc $_[1] while @_ = each %$hash_ref;
$hash_ref = \%lc_hash;

print Dumper $hash_ref;

__END__
[download]

Thank You,
Charles K. Clarkson

Comment on How do I convert entire hash to lowercase? Download Code

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Re: How do I convert entire hash to lowercase? by japhy (Canon) on Nov 18, 2001 at 11:50 UTC
(Updated.) I'd do this: `@hash{map lc, @k} = map lc, delete @hash{@k = keys %hash};` [download] Nifty? _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker. `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply] [d/l]
Re: Re: How do I convert entire hash to lowercase? by data64 (Chaplain) on Nov 18, 2001 at 21:49 UTC
I don't think I completely understand how exactly this piece of code works. Can someone explain ? thanks.	[reply]
Re: Re: Re: How do I convert entire hash to lowercase? by japhy (Canon) on Nov 18, 2001 at 23:20 UTC
I think I can... `# @hash{map lc, @k} = # map lc, delete @hash{@k = keys %hash}; @keys = keys %hash; @lc_values = map { lc $_ } @hash{@keys}; # hash slice @lc_keys = map { lc $_ } @keys; delete @hash{@keys}; # basically: %hash = () @hash{@lc_keys} = @lc_values;` [download] </code> _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker. `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply] [d/l]
Re: How do I convert entire hash to lowercase? by chipmunk (Parson) on Nov 18, 2001 at 22:01 UTC
This is similar to japhy's solution, but a little more straightforward: `%hash = map lc, %hash;`	[reply] [d/l]
Re: Re: How do I convert entire hash to lowercase? by chromatic (Archbishop) on Nov 19, 2001 at 00:57 UTC
Very nice! Let's make it work on a hash reference: `$h_ref = { map lc, %$h_ref };` For those of you who don't quite follow, here are the rules: In list context, a hash returns a list of key => value pairs. This is the same thing you use when you create a hash. There's no guaranteed order, though, which is rather the point. map iterates over the elements of a list, applies some transformation to each, and produces an equally-sized list of the results. `map lc, %list` iterates over the keys and values of the hash (by design, a value follows its key) and lowercases each. The right side of the expression is evaluated first, so the same variable can be used on both sides. Wrapping the map statement in curly braces turns the resulting list into an anonymous hash.</li. Assigning that to the original hash reference makes sure the old, potentially upper-cased keys and values are no longer there. You can get by without the anonymous hash construction, but I thought it was more clear. map is nice.	[reply] [d/l] [select]
Re: Re: How do I convert entire hash to lowercase? by japhy (Canon) on Nov 19, 2001 at 01:00 UTC
Oh, duh. _____________________________________________________ Jeff`[japhy]`Pinyan: Perl, regex, and perl hacker. `s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;`	[reply]
Re: How do I convert entire hash to lowercase? by Zaxo (Archbishop) on Nov 18, 2001 at 12:40 UTC
Sure, you have a reference; you can modify it. I don't know if this is exactly what you want. It doesn't allow for keys which differ only by case having different values: `sub DeAOL { for ( keys %{$_[0]} ) { my $tmp = lc $_[0]->{$_}; delete $_[0]->{$_}; $_[0]->{lc $_} = $tmp; } }` [download] After Compline, Zaxo	[reply] [d/l]


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