Tie::IxHash(3)						User Contributed Perl Documentation					    Tie::IxHash(3)

NAME

       Tie::IxHash - ordered associative arrays for Perl

SYNOPSIS

	   # simple usage
	   use Tie::IxHash;
	   tie HASHVARIABLE, Tie::IxHash [, LIST];

	   # OO interface with more powerful features
	   use Tie::IxHash;
	   TIEOBJECT = Tie::IxHash->new( [LIST] );
	   TIEOBJECT->Splice( OFFSET [, LENGTH [, LIST]] );
	   TIEOBJECT->Push( LIST );
	   TIEOBJECT->Pop;
	   TIEOBJECT->Shift;
	   TIEOBJECT->Unshift( LIST );
	   TIEOBJECT->Keys( [LIST] );
	   TIEOBJECT->Values( [LIST] );
	   TIEOBJECT->Indices( LIST );
	   TIEOBJECT->Delete( [LIST] );
	   TIEOBJECT->Replace( OFFSET, VALUE, [KEY] );
	   TIEOBJECT->Reorder( LIST );
	   TIEOBJECT->SortByKey;
	   TIEOBJECT->SortByValue;
	   TIEOBJECT->Length;

DESCRIPTION

       This Perl module implements Perl hashes that preserve the order in which the hash elements were added.  The order is not affected when
       values corresponding to existing keys in the IxHash are changed.  The elements can also be set to any arbitrary supplied order.	The
       familiar perl array operations can also be performed on the IxHash.

   Standard "TIEHASH" Interface
       The standard "TIEHASH" mechanism is available. This interface is recommended for simple uses, since the usage is exactly the same as
       regular Perl hashes after the "tie" is declared.

   Object Interface
       This module also provides an extended object-oriented interface that can be used for more powerful operations with the IxHash.  The
       following methods are available:

       FETCH, STORE, DELETE, EXISTS
	       These standard "TIEHASH" methods mandated by Perl can be used directly.	See the "tie" entry in perlfunc(1) for details.

       Push, Pop, Shift, Unshift, Splice
	       These additional methods resembling Perl functions are available for operating on key-value pairs in the IxHash. The behavior is
	       the same as the corresponding perl functions, except when a supplied hash key already exists in the hash. In that case, the
	       existing value is updated but its order is not affected.  To unconditionally alter the order of a supplied key-value pair, first
	       "DELETE" the IxHash element.

       Keys    Returns an array of IxHash element keys corresponding to the list of supplied indices.  Returns an array of all the keys if called
	       without arguments.  Note the return value is mostly only useful when used in a list context (since perl will convert it to the
	       number of elements in the array when used in a scalar context, and that may not be very useful).

	       If a single argument is given, returns the single key corresponding to the index.  This is usable in either scalar or list context.

       Values  Returns an array of IxHash element values corresponding to the list of supplied indices.  Returns an array of all the values if
	       called without arguments.  Note the return value is mostly only useful when used in a list context (since perl will convert it to
	       the number of elements in the array when used in a scalar context, and that may not be very useful).

	       If a single argument is given, returns the single value corresponding to the index.  This is usable in either scalar or list
	       context.

       Indices Returns an array of indices corresponding to the supplied list of keys.	Note the return value is mostly only useful when used in a
	       list context (since perl will convert it to the number of elements in the array when used in a scalar context, and that may not be
	       very useful).

	       If a single argument is given, returns the single index corresponding to the key.  This is usable in either scalar or list context.

       Delete  Removes elements with the supplied keys from the IxHash.

       Replace Substitutes the IxHash element at the specified index with the supplied value-key pair.	If a key is not supplied, simply
	       substitutes the value at index with the supplied value. If an element with the supplied key already exists, it will be removed from
	       the IxHash first.

       Reorder This method can be used to manipulate the internal order of the IxHash elements by supplying a list of keys in the desired order.
	       Note however, that any IxHash elements whose keys are not in the list will be removed from the IxHash.

       Length  Returns the number of IxHash elements.

       SortByKey
	       Reorders the IxHash elements by textual comparison of the keys.

       SortByValue
	       Reorders the IxHash elements by textual comparison of the values.

EXAMPLE

	   use Tie::IxHash;

	   # simple interface
	   $t = tie(%myhash, Tie::IxHash, 'a' => 1, 'b' => 2);
	   %myhash = (first => 1, second => 2, third => 3);
	   $myhash{fourth} = 4;
	   @keys = keys %myhash;
	   @values = values %myhash;
	   print("y") if exists $myhash{third};

	   # OO interface
	   $t = Tie::IxHash->new(first => 1, second => 2, third => 3);
	   $t->Push(fourth => 4); # same as $myhash{'fourth'} = 4;
	   ($k, $v) = $t->Pop;	  # $k is 'fourth', $v is 4
	   $t->Unshift(neg => -1, zeroth => 0);
	   ($k, $v) = $t->Shift;  # $k is 'neg', $v is -1
	   @oneandtwo = $t->Splice(1, 2, foo => 100, bar => 101);

	   @keys = $t->Keys;
	   @values = $t->Values;
	   @indices = $t->Indices('foo', 'zeroth');
	   @itemkeys = $t->Keys(@indices);
	   @itemvals = $t->Values(@indices);
	   $t->Replace(2, 0.3, 'other');
	   $t->Delete('second', 'zeroth');
	   $len = $t->Length;	  # number of key-value pairs

	   $t->Reorder(reverse @keys);
	   $t->SortByKey;
	   $t->SortByValue;

BUGS

       You cannot specify a negative length to "Splice". Negative indexes are OK, though.

       Indexing always begins at 0 (despite the current $[ setting) for all the functions.

TODO

       Addition of elements with keys that already exist to the end of the IxHash must be controlled by a switch.

       Provide "TIEARRAY" interface when it stabilizes in Perl.

       Rewrite using XSUBs for efficiency.

AUTHOR

       Gurusamy Sarathy        gsar@umich.edu

       Copyright (c) 1995 Gurusamy Sarathy. All rights reserved.  This program is free software; you can redistribute it and/or modify it under
       the same terms as Perl itself.

VERSION

       Version 1.22    27 February 2010

SEE ALSO

       perl(1)

perl v5.12.1							    2010-02-27							    Tie::IxHash(3)