Tie::CPHash - Case preserving but case insensitive hash table
This document describes version 2.000 of
Tie::CPHash, released January 17, 2015.
use Tie::CPHash 2; # allows initialization during tie
tie %cphash, 'Tie::CPHash', key => 'value';
$cphash{'Hello World'} = 'Hi there!';
printf("The key `%s' was used to store `%s'.\n",
tied(%cphash)->key('HELLO WORLD'),
$cphash{'HELLO world'});
The Tie::CPHash module provides a hash table that is case
preserving but case insensitive. This means that
$cphash{KEY} $cphash{key}
$cphash{Key} $cphash{keY}
all refer to the same entry. Also, the hash remembers which form of
the key was last used to store the entry. The keys and each
functions will return the key that was used to set the value.
An example should make this clear:
tie %h, 'Tie::CPHash', Hello => 'World';
print $h{HELLO}; # Prints 'World'
print keys(%h); # Prints 'Hello'
$h{HELLO} = 'WORLD';
print $h{hello}; # Prints 'WORLD'
print keys(%h); # Prints 'HELLO'
Tie::CPHash version 2.000 introduced the ability to pass a list of
key => value pairs to initialize the hash (along with the
add method that powers it). The list must include a value for
each key, or the constructor will croak.
The additional key method lets you fetch the case of a specific key:
# When run after the previous example, this prints 'HELLO':
print tied(%h)->key('Hello');
(The tied function returns the object that %h is tied to.)
If you need a case insensitive hash, but don't need to preserve case,
just use $hash{lc $key} instead of $hash{$key}. This has a lot
less overhead than Tie::CPHash.
use Tie::CPHash; does not export anything into your namespace.
tied(%h)->add( key => value, ... );
tied(%h)->add( \@list_of_key_value_pairs );
This method (introduced in version 2.000) adds keys and values to the hash.
It's just like
%h = @list_of_key_value_pairs;
except that it doesn't clear the hash first. It accepts either a list
or an arrayref. It croaks if the list has an odd number of entries.
It returns the tied hash object.
If the list contains duplicate keys, the last key => value
pair in the list wins. (You can't pass a hashref to add because it
would be ambiguous which key would win if two keys differed only in case.)
For people used to the Tie::IxHash manpage, add is aliased to both Push
and Unshift. (Tie::CPHash does not preserve the order of keys.)
$set_using_key = tied(%h)->key( $key )
This method lets you fetch the case of a specific key. For example:
$h{HELLO} = 'World';
print tied(%h)->key('Hello'); # prints HELLO
If the key does not exist in the hash, it returns undef.
- Odd number of elements in CPHash add
-
You passed a list with an odd number of elements to the
add method
(or to tie, which uses add).
The list must contain a value for each key.
Tie::CPHash requires no configuration files or environment variables.
None reported.
No bugs have been reported.
Christopher J. Madsen <perl AT cjmweb.net>
Please report any bugs or feature requests
to <bug-Tie-CPHash AT rt.cpan.org>
or through the web interface at
http://rt.cpan.org/Public/Bug/Report.html.
You can follow or contribute to Tie-CPHash's development at
https://github.com/madsen/tie-cphash.
This software is copyright (c) 2015 by Christopher J. Madsen.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
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