Sorting algorithms/Bubble sort: Difference between revisions

===Alternative version===

Should be ISO (but tested only with GNU Prolog).

Note: doesn't constuct list for each swap, only for each pass.

<lang prolog>:- initialization(main).

bubble_sort(Xs,Res) :-

write(Xs), nl

, bubble_pass(Xs,Ys,Changed)

, ( Changed == true -> bubble_sort(Ys,Res) ; Res = Ys )

.

bubble_pass(Xs,Res,Changed) :-

Xs = [X|Ys], Ys = [Y|Zs]

, ( X > Y -> H = Y, T = [X|Zs], Changed = true

; H = X, T = Ys

)

, Res = [H|R], bubble_pass(T,R,Changed)

; Res = Xs

.

test([8,9,1,3,4,2,6,5,4]).

main :- test(T), bubble_sort(T,_), halt.</lang>

{{Output}}

<pre>[8,9,1,3,4,2,6,5,4]

[8,1,3,4,2,6,5,4,9]

[1,3,4,2,6,5,4,8,9]

[1,3,2,4,5,4,6,8,9]

[1,2,3,4,4,5,6,8,9]</pre>