Heap(3) | User Contributed Perl Documentation | Heap(3) |

# NAME¶

Heap - Perl extensions for keeping data partially sorted

# SYNOPSIS¶

use Heap; my $heap = Heap->new; my $elem; use Heap::Elem::Num(NumElem); foreach $i ( 1..100 ) { $elem = NumElem( $i ); $heap->add( $elem ); } while( defined( $elem = $heap->extract_top ) ) { print "Smallest is ", $elem->val, "\n"; }

# DESCRIPTION¶

The Heap collection of modules provide routines that manage a heap of elements. A heap is a partially sorted structure that is always able to easily extract the smallest of the elements in the structure (or the largest if a reversed compare routine is provided).

If the collection of elements is changing dynamically, the heap has less overhead than keeping the collection fully sorted.

The elements must be objects as described in
"Heap::Elem" and all elements inserted into one heap must be
mutually compatible - either the same class exactly or else classes that
differ only in ways unrelated to the **Heap::Elem** interface.

# METHODS¶

- $heap =
**HeapClass::new()**; $heap2 = $heap1->**new()**; - Returns a new heap object of the specified (sub-)class. This is often used as a subroutine instead of a method, of course.
- $heap->DESTROY
- Ensures that no internal circular data references remain. Some variants of Heap ignore this (they have no such references). Heap users normally need not worry about it, DESTROY is automatically invoked when the heap reference goes out of scope.
- $heap->add($elem)
- Add an element to the heap.
- $elem = $heap->top
- Return the top element on the heap. It is
**not**removed from the heap but will remain at the top. It will be the smallest element on the heap (unless a reversed cmp function is being used, in which case it will be the largest). Returns*undef*if the heap is empty.This method used to be called "minimum" instead of "top". The old name is still supported but is deprecated. (It was confusing to use the method "minimum" to get the maximum value on the heap when a reversed cmp function was used for ordering elements.)

- $elem = $heap->extract_top
- Delete the top element from the heap and return it. Returns
*undef*if the heap was empty.This method used to be called "extract_minimum" instead of "extract_top". The old name is still supported but is deprecated. (It was confusing to use the method "extract_minimum" to get the maximum value on the heap when a reversed cmp function was used for ordering elements.)

- $heap1->absorb($heap2)
- Merge all of the elements from
*$heap2*into*$heap1*. This will leave*$heap2*empty. - $heap1->decrease_key($elem)
- The element will be moved closed to the top of the heap if it is now
smaller than any higher parent elements. The user must have changed the
value of
*$elem*before*decrease_key*is called. Only a decrease is permitted. (This is a decrease according to the*cmp*function - if it is a reversed order comparison, then you are only permitted to increase the value of the element. To be pedantic, you may only use*decrease_key*if*$elem**-*cmp($elem_original) <= 0> if*$elem_original*were an elem with the value that*$elem*had before it was*decreased*.) - $elem = $heap->delete($elem)
- The element is removed from the heap (whether it is at the top or not).

# AUTHOR¶

John Macdonald, john@perlwolf.com

# COPYRIGHT¶

Copyright 1998-2007, O'Reilly & Associates.

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

# SEE ALSO¶

**Heap::Elem**(3), **Heap::Binary**(3),
**Heap::Binomial**(3), **Heap::Fibonacci**(3).

2020-10-28 | perl v5.40.0 |