Perl Diver 2.31
Main Environment Variables Perl Default Values Perl Config - Summary Perl Config - Full Installed Modules List Directory uptime Docs

Module Documentation
Details and documentation about a specific module, including version and documentation (if available). Note that while links to perldoc.com and search.cpan.org are provided, the module may be part of a larger distribution. If you reach a File Not Found page on either site, please try the parent module.

Heap071::Elem

Name Heap071::Elem
Version
Located at /usr/share/perl5/vendor_perl
File /usr/share/perl5/vendor_perl/Heap071/Elem.pm
Is Core No
Search CPAN for this module Heap071::Elem
Documentation Heap071::Elem
Module Details Heap071::Elem

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 provides 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 routines. 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.

The Heap processing routines will ensure that this value is undef when this elem is removed from a heap, and is not undef after it is inserted into a heap. This means that you can check whether an element is currently contained within a heap or not. (It cannot be used to determine which heap an element is contained in, if you have multiple heaps. Keeping that information accurate would make the operation of merging two heaps into a single one take longer - it would have to traverse all of the elements in the merged heap to update them; for Binomial and Fibonacci heaps that would turn an O(1) operation into an O(n) one.)

$elem1->cmp($elem2)
A routine to compare two elements. It must return a negative value if this element should go higher on the heap than $elem2, 0 if they are equal, or a positive value if this element should go lower on the heap than $elem2. Just as with sort, the Perl operators <=> and cmp cause the smaller value to be returned first; similarly you can negate the meaning to reverse the order - causing the heap to always return the largest element instead of the smallest.


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 key of heap, leaving it unchanged for use by the heap routines, then the following implementation 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@perlwolf.com


COPYRIGHT

Copyright 1998-2003, O'Reilly & Associates.

This code is distributed under the same copyright terms as perl itself.


SEE ALSO

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

Perl Diver brought to you by ScriptSolutions.com © 1997- 2024