Franï¿½ois Pinard wrote:

> By the way, what is a "heap type"?
I don't know, but:

http://foldoc.doc.ic.ac.uk/foldoc/fo...&action=Search
heap

1. <programming> An area of memory used for dynamic memory allocation

where blocks of memory are allocated and freed in an arbitrary order and

the pattern of allocation and size of blocks is not known until run

time. Typically, a program has one heap which it may use for several

different purposes.

Heap is required by languages in which functions can return arbitrary

data structures or functions with free variables (see closure). In C

functions malloc and free provide access to the heap.

Contrast stack. See also dangling pointer.

2. <programming> A data structure with its elements partially ordered

(sorted) such that finding either the minimum or the maximum (but not

both) of the elements is computationally inexpensive (independent of the

number of elements), while both adding a new item and finding each

subsequent smallest/largest element can be done in O(log n) time, where

n is the number of elements.

Formally, a heap is a binary tree with a key in each node, such that all

the leaves of the tree are on two adjacent levels; all leaves on the

lowest level occur to the left and all levels, except possibly the

lowest, are filled; and the key in the root is at least as large as the

keys in its children (if any), and the left and right subtrees (if they

exist) are again heaps.

Note that the last condition assumes that the goal is finding the

minimum quickly.

Heaps are often implemented as one-dimensional arrays. Still assuming

that the goal is finding the minimum quickly the invariant is

heap[i] <= heap[2*i] and heap[i] <= heap[2*i+1] for all i,

where heap[i] denotes the i-th element, heap[1] being the first.

Heaps can be used to implement priority queues or in sort algorithms.

And:

http://www.python.org/dev/doc/devel/...ule-heapq.html
Heaps are arrays for which heap[k] <= heap[2*k+1] and heap[k] <=

heap[2*k+2] for all k, counting elements from zero. For the sake of

comparison, non-existing elements are considered to be infinite. The

interesting property of a heap is that heap[0] is always its smallest

element.

Gerrit.

--

PrePEP: Builtin path type

http://people.nl.linux.org/~gerrit/c.../pep-xxxx.html
Asperger's Syndrome - a personal approach:

http://people.nl.linux.org/~gerrit/english/