总是可以定义更笼统的谓词并以狭窄的方式使用它:

Always good to define more general predicate and use it in a narrowed fashion:

perm(X,L):- mselect(X,L,[]).

mselect([A|B],L,R):- select(A,L,M), mselect(B,M,R).
mselect([],L,L).

member不好，因为它使第二个列表保持不变. delete也不好，因为它删除了多重性.

member is no good as it leaves the second list unchanged. delete is no good either as it deletes the multiplicities.

您可以使用append. :)它也结合了选择和删除:

You could use append though. :) It too combines picking and removing:

perm([A|B],L):- length(L,N), between(0,N,I),length(X,I),
  append(X,[A],Y), append(Y,Z,L),
  append(X,Z,M), perm(B,M).
perm([],[]).