setof/3 problem #3151
Description
?- L=[_,_,_,_], setof(t,permutation(L,L),_).
L = [_A,_B,_C,_D]
; L = [_A,_B,_C,_C]
; L = [_A,_B,_B,_C]
; L = [_A,_B,_B,_B]
; L = [_A,_B,_C,_B]
; L = [_A,_A,_B,_C]
; L = [_A,_A,_B,_B]
; L = [_A,_A,_A,_B]
; L = [_A,_A,_A,_A]
; L = [_A,_A,_B,_A]
; L = [_A,_A,_A,_B], unexpected
; L = [_A,_A,_A,_A], unexpected
; L = [_A,_B,_A,_C]
; L = [_A,_B,_A,_A]
; L = [_A,_B,_A,_B]
; L = [_A,_A,_A,_A], unexpected
; L = [_A,_A,_B,_A], unexpected
; L = [_A,_B,_A,_A], unexpected
; L = [_A,_B,_C,_A]
; L = [_A,_A,_A,_A], unexpected
; L = [_A,_B,_B,_A].
(Thus, there are still some redundant leaf answers. Also the order might be a different one. I found this while preparing my slides — checking, just in case...)