Problem with delayed goals

[Neztov]

Hello,

I'm trying to solve the Japanese puzzle kuromasu with prolog (Eclipse clp).

http://en.wikipedia.org/wiki/Kuromasu

In this game you have to colour every cell of a grid black or white.
One of this game constraints is that you may not have two black cells next to each other. (this is atm the only constraint I have programmed)

My idea in programming this with prolog was to make a WhiteList and a BlackList.
These consist of all the cells who are white/black.

Initially you know only that the numbered cells are white.
So I suspend the other cells of being a member of either WhiteList or BlackList.

The initial creation (create_puzzle) works fine and and with 17 delayed goals exactly as expected.

The problem start when I'm putting the constraints on my lists. For example if I say no_neighbours(BlackList) this results in an empty list, because it doesn't wait until the delayed goals are solved.

What I like to find out is a way that every time the search function labels a new cell to be black it checks if the BlackList has no_neighbours.

I know this is quite an open question but any suggestion is welcome, even if it is a completely different perspective.

This is my code so far:

:- lib(ic).
:- lib(lists).
:- lib(arrays).

kuromasu(Id, Board, BlackList, WhiteList) :-
	puzzle(Id, Dim, NumberList),
	create_puzzle(NumberList, Dim, Board, BlackList, WhiteList),
	constraints(Board, NumberList, BlackList, WhiteList, Dim),
	search(Board),
	print_board(Board).


create_puzzle(NumberList, Dim, Board, BlackList, WhiteList) :-
	dim(Board, [Dim,Dim]),
	
	( foreach((I,J,Value), NumberList),
	  param(Board)
	do
		subscript(Board,[I,J],0)
	),
	Board :: [0..1],
	( for(I,1,Dim),
	  param(Dim,Board, BlackList,WhiteList)
	do
		( for(J,1,Dim),
		  param(Dim,I,Board,BlackList,WhiteList)
		do
			Box is Board[I,J],
			( var(Box) ->
				suspend(				
				( Box =:= 0 ->
					memberchk((I,J),WhiteList)
				;
					memberchk((I,J),BlackList)
				),2, Box->inst)
			;
				( Box =:= 0 ->
					memberchk((I,J),WhiteList)
				;
					memberchk((I,J),BlackList)
				)
			)
		)
	).
	
constraints(Board, NumberList, BlackList, WhiteList, Dim) :-
	no_neighbours(BlackList).	


no_neighbours(X:[]).
no_neighbours((X,Y):Xs) :-
	nonmember((X+1,Y),Xs),
	nonmember((X-1,Y),Xs),
	nonmember((X,Y+1),Xs),
	nonmember((X,Y-1),Xs),
	no_neighbours(Xs).




search(Values) :-
    term_variables(flatten(Values), Vars),
    labeling(flatten(Values)).

print_board(Board) :-
	( foreachelem(El,Board,[_,J])
	do
		( J=:= 1 -> nl ; true),
		write(' '),
		(var(El) -> write('_') ; write(El) )
	).

puzzle(1,5,[ (2,1,8),(2,3,8),(2,5,5),(3,2,7),(3,4,7),(4,1,8),(4,3,8),(4,5,6)]).

Thanks in advance.