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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.

       Clear   Resets the IxHash to its	pristine state:	with no	elements at
	       all.

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.

NOTE
       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 1.23

SEE ALSO
       perl(1)

perl v5.32.0			  2013-02-24			Tie::IxHash(3)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | BUGS | NOTE | TODO | AUTHOR | VERSION | SEE ALSO

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