elem(3)

NAME

Heap::Elem - Perl extension for elements to be put in
Heaps

SYNOPSIS

use Heap::Elem::SomeInheritor;
use Heap::SomeHeapClass;
$elem = Heap::Elem::SomeInheritor->new( $value );
$heap = Heap::SomeHeapClass->new;
$heap->add($elem);

DESCRIPTION

This is an inheritable class for Heap Elements. It pro
vides the interface documentation and some inheritable
methods. Only a child classes can be used - this class is
not complete.

METHODS

$elem = Heap::Elem::SomeInheritor->new( [args] );

Creates a new Elem.

$elem->heap( $val ); $elem->heap;

Provides a method for use by the Heap processing rou
tines. If a value argument is provided, it will be
saved. The new saved value is always returned. If no
value argument is provided, the old saved value is
returned.

The Heap processing routines use this method to map an
element into its internal structure. This is needed
to support the Heap methods that affect elements that
are not are the top of the heap - decrease_key and delete.

$elem1->cmp($elem2)

A routine to compare two elements. It must return a
negative value if this element is less than $elem2, 0
if they are equal, or a positive value if this element
is greater than $elem2. Just as with sort, you can
negate the meaning to reverse the order - causing the
heap to always return the largest element instead of
the smallest. (That does make the Heap method names
minimum, extract_minimum, and decrease_key counter-intuitive, though.)

INHERITING

This class can be inherited to provide an oject with the
ability to be heaped. If the object is implemented as a
hash, and if it can deal with a kay of heap, leaving it
unchanged for use by the heap routines, then the following
implemetation will work.

package myObject;

require Exporter;

@ISA = qw(Heap::Elem);

sub new {

my $self = shift;
my $class = ref($self) || $self;

my $self = SUPER::new($class);

# set $self->{key} = $value;

}

sub cmp {

my $self = shift;
my $other = shift;

$self->{key} cmp $other->{key};

}

# other methods for the rest of myObject's functionality

AUTHOR

John Macdonald, jmm@elegant.com

SEE ALSO

Heap(3), Heap::Elem::Num(3), Heap::Elem::NumRev(3), Heap::Elem::Str(3), Heap::Elem::StrRev(3).

perl v5.8.0 1998-04-28 Elem(3)