=encoding utf8

=head1 NAME

Hash::Case - base class for hashes with key-casing requirements

=head1 INHERITANCE

 Hash::Case
   is a Tie::StdHash

 Hash::Case is extended by
   Hash::Case::Lower
   Hash::Case::Preserve
   Hash::Case::Upper

=head1 SYNOPSIS

 use Hash::Case::Lower;
 tie my(%lchash), 'Hash::Case::Lower';
 $lchash{StraNGeKeY} = 3;
 print keys %lchash;  # strangekey

=head1 DESCRIPTION

Hash::Case is the base class for various classes which tie special
treatment for the casing of keys.  Be aware of the differences in
implementation: C<Lower> and C<Upper> are tied native hashes:
these hashes have no need for hidden fields or other assisting
data structured.  A case C<Preserve> hash will actually create
three hashes.

The following strategies are implemented:

=over 4

=item * Hash::Case::Lower (native hash)

Keys are always considered lower case. The internals of this
module translate any incoming key to lower case before it is used.

=item * Hash::Case::Upper (native hash)

Like the ::Lower, but then all keys are always translated into
upper case.  This module can be of use for some databases, which
do translate everything to capitals as well.  To avoid confusion,
you may want to have you own internal Perl hash do this as well.

=item * Hash::Case::Preserve

The actual casing is ignored, but not forgotten.

=back

=head1 METHODS

=head2 Constructors

=over 4

=item $obj-E<gt>B<addHashData>(HASH)

Add the data of a hash (passed as reference) to the created tied hash.  The
existing values in the hash remain, the keys are adapted to the needs of the
the casing.

=item $obj-E<gt>B<addPairs>(PAIRS)

Specify an even length list of alternating key and value to be stored in
the hash.

=item $obj-E<gt>B<setHash>(HASH)

The functionality differs for native and wrapper hashes.  For native
hashes, this is the same as first clearing the hash, and then a call
to L<addHashData()|Hash::Case/"Constructors">.  Wrapper hashes will use the hash you specify here
to store the data, and re-create the mapping hash.

=item B<tie>(HASH, TIE, [VALUES,] OPTIONS)

Tie the HASH with the TIE package which extends L<Hash::Case>.  The OPTIONS
differ per implementation: read the manual page for the package you actually
use.  The VALUES is a reference to an array containing key-value pairs,
or a reference to a hash: they fill the initial hash.

example: 

 my %x;
 tie %x, 'Hash::Case::Lower';
 $x{Upper} = 3;
 print keys %x;       # 'upper'

 my @y = (ABC => 3, DeF => 4);
 tie %x, 'Hash::Case::Lower', \@y;
 print keys %x;       # 'abc' 'def'

 my %z = (ABC => 3, DeF => 4);
 tie %x, 'Hash::Case::Lower', \%z;

=back

=head1 SEE ALSO

This module is part of Hash-Case distribution version 1.03,
built on January 22, 2018. Website: F<http://perl.overmeer.net/CPAN/>

=head1 LICENSE

Copyrights 2002-2018 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://dev.perl.org/licenses/>