1% generated: 16 November 1989
2% option(s): SOURCE_TRANSFORM_1
3%
4%   qsort
5%
6%   David H. D. Warren
7%   Copyright: Public domain
8%
9%   quicksort a list of 50 integers
10
11top:-qsort.
12
13qsort :- qsort([27,74,17,33,94,18,46,83,65, 2,
14		32,53,28,85,99,47,28,82, 6,11,
15		55,29,39,81,90,37,10, 0,66,51,
16		 7,21,85,27,31,63,75, 4,95,99,
17		11,28,61,74,18,92,40,53,59, 8],_,[]).
18
19qsort([X|L],R,R0) :-
20	partition(L,X,L1,L2),
21	qsort(L2,R1,R0),
22	qsort(L1,R,[X|R1]).
23qsort([],R,R).
24
25partition([X|L],Y,[X|L1],L2) :-
26	X =< Y, !,
27	partition(L,Y,L1,L2).
28partition([X|L],Y,L1,[X|L2]) :-
29	partition(L,Y,L1,L2).
30partition([],_,[],[]).
31