phpman > perldoc > 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 AT 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).