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 inter
face 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 corre
sponding 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 corre
- sponding to the list of supplied indices. Returns
an array of all the keys if called without argu
ments. Note the return value is mostly only use
ful 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 corre
- sponding to the list of supplied indices. Returns
an array of all the values if called without argu
ments. Note the return value is mostly only use
ful 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 ele
ments 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 $[ set
ting) 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