% List permutor example 
%:-module listpermutor.
%:-public listPermutor/2, listPermute/2.
%:-public test_perm.

listSelector(S,List):-
	assignable(S, list(List,[])).	
listSelect(S,E,Rest1):-
	S=>list([E|Rest],Rest0),!,
	S<+list(Rest,[E|Rest0]),
	append(Rest0,Rest,Rest1).	% not so smart yet
append([A|L],E,[A|R]):-!,append(L,E,R).
append([],E,E).

listPermutor(P,List):-
	listSelector(S,List),
	listSelect(S,E,Rest),
	listPermutor(R,Rest), !,
	assignable(P, perm(S,E,R)).
listPermutor(P,[]):-
	assignable(P, []) .
listPermute(P,[E|Perm]):-
	P=>perm(_,E,R),
	listPermute(R,Perm),!.
listPermute(P,[]):-
	P => [],!,
	P <+ end.
listPermute(P,Perm):-
	P=>perm(S,_,_),
	listSelect(S,E,Rest),
	listPermutor(R,Rest),!,
	P<+perm(S,E,R),
	listPermute(P,Perm).

test_perm:-
	listPermutor(P,[a,b,c]),
	listPermute(P,L1),
	write(L1),nl,
	listPermute(P,L2),
	write(L2),nl,
	listPermute(P,L3),
	write(L3),nl,
	listPermute(P,L4),
	write(L4),nl,
	listPermute(P,L5),
	write(L5),nl,
	listPermute(P,L6),
	write(L6),nl,
	listPermute(P,L7),	% fails
	write(L7),nl.