I would like to get this result:
?- numberMatrixLines(1,[[1,1,1,1,1,1,1,1],[1,1,1,1,1,1,1,1],[1,1,1,1,1,1,1,1]],X).
X = [machinePenalty(1,[1,1,1,1,1,1,1,1]),
machinePenalty(2 [1,1,1,1,1,1,1,1]),
machinePenalty(3,[1,1,1,1,1,1,1,1])]
I try the following code:
numberMatrixLines(X,[],ResultMatrix):-
writeln('should end here'),
reverse(ResultMatrix,ResultMatrixTemp),
initWith(ResultMatrixTemp,ResultMatrix),
!.
numberMatrixLines(X,[H|T],ResultMatrix):-
append_in_front(machinePenalty(X,H),ResultMatrix,ResultMatrixTemp),
writeln(ResultMatrixTemp),
incr(X,X1),
numberMatrixLines(X1,T,ResultMatrixTemp).
incr(X, X1) :-
X1 is X+1.
append_in_front(X,[],[X]).
append_in_front(X,L1,[X|L1]).
The result is correct when numberMatrixLines(X,[],ResultMatrix) is reached. HOWEVER, the predicate won't stop there and return X , as it's supposed to.
What can be done to make it stop in that line?
A straight-forward solution would be (I moved the input list to the first argument to take advantage of Prolog first-argument indexing to avoid spurious choice-points and the need of cuts):
% number_matrix_lines(+list, +integer, -list)
number_matrix_lines([], _, []).
number_matrix_lines([Line| Lines], I, [machine_penalty(I,Line)| NumberLines]) :-
J is I + 1,
number_matrix_lines(Lines, J, NumberLines).
Sample call:
| ?- number_matrix_lines([[1,1,1,1,1,1,1,1],[1,1,1,1,1,1,1,1],[1,1,1,1,1,1,1,1]], 1, NumberLines).
NumberLines = [machine_penalty(1,[1,1,1,1,1,1,1,1]), machine_penalty(2,[1,1,1,1,1,1,1,1]), machine_penalty(3,[1,1,1,1,1,1,1,1])]
yes
P.S. Note that Prolog coding guidelines advise using underscores in predicate names instead of CamelCase.