Quicksort

A sorting algorithm with O(n log n) average time

complexity.

One element, x of the list to be sorted is chosen and the

other elements are split into those elements less than x and

those greater than or equal to x. These two lists are then

sorted recursively using the same algorithm until there is

only one element in each list, at which point the sublists are

recursively recombined in order yielding the sorted list.

This can be written in Haskell:

qsort :: Ord a =@# [a] -@# [a]

qsort [] = []

qsort (x:xs) = qsort [ u | u#@-xs, u#@x ] ++

[ x ] ++

qsort [ u | u-xs, u=x ]

[Mark Jones, Gofer prelude.]