Tie::IxHash(3) User Contributed Perl Documentation Tie::IxHash(3)NAMETie::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 recom‐
mended 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 follow‐
ing 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 avail‐
able for operating on key-value pairs in the IxHash. The behav‐
ior 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 corre‐
sponding 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 con‐
vert 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 corre‐
sponding 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 corre‐
sponding 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 sub‐
stitutes the value at index with the supplied value. If an ele‐
ment 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 val‐
ues.
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 1.21 20 Nov 1997
SEE ALSOperl(1)perl v5.8.0 1997-11-20 Tie::IxHash(3)
