Why “…” appears in my answer of matrix in Prolog

Question

I made a little code for creating a matrix of coordinates (like a chessboard), it's the following:

createMatrix(N,M,R) :- creaMatriu(N,M,A), reversed(R,A).
creaMatriu(N,0,[T]) :- creafila(N,0,T),!.
creaMatriu(N,M,[T|C]) :- creafila(N,M,T), M1 is M-1, creaMatriu(N,M1,C).
creafila(0,M,[[M,0]]):-!.
creafila(N,M,[[M,N]|C]) :-N1 is N-1,creafila(N1,M,C).
reversed(A, B) :- reversed(B, [], A).
reversed([A|B], C, D) :- reverse(N,A),reversed(B, [N|C], D).
reversed([], A, A).

The first time I executed it went well, but when i incremented the dimensions of the matrix, the "dots" at the end of the matrix begin to appear incrementing one coordinate as the dimension rises, as like this:

?- createMatrix(1,1,R).
R = [[[0, 0], [0, 1]], [[1, 0], [1, 1]]] .

?- createMatrix(2,1,R).
R = [[[0, 0], [0, 1], [0, 2]], [[1, 0], [1, 1], [1, 2]]] .

?- createMatrix(2,2,R).
R = [[[0, 0], [0, 1], [0, 2]], [[1, 0], [1, 1], [1, 2]], [[2, 0], [2, 1], [2, 2]]] .

?- createMatrix(3,2,R).
R = [[[0, 0], [0, 1], [0, 2], [0, 3]], [[1, 0], [1, 1], [1, 2], [1, 3]], [[2, 0], [2, 1], [2, 2], [2, 3]]] .

?- createMatrix(3,3,R).
R = [[[0, 0], [0, 1], [0, 2], [0, 3]], [[1, 0], [1, 1], [1, 2], [1, 3]], [[2, 0], [2, 1], [2, 2], [2, 3]], [[3, 0], [3, 1], [3, 2], [3|...]]] .

?- createMatrix(4,3,R).
R = [[[0, 0], [0, 1], [0, 2], [0, 3], [0, 4]], [[1, 0], [1, 1], [1, 2], [1, 3], [1, 4]], [[2, 0], [2, 1], [2, 2], [2, 3], [2|...]], [[3, 0], [3, 1], [3, 2], [3|...], [...|...]]] .

?- createMatrix(4,4,R).
R = [[[0, 0], [0, 1], [0, 2], [0, 3], [0, 4]], [[1, 0], [1, 1], [1, 2], [1, 3], [1, 4]], [[2, 0], [2, 1], [2, 2], [2, 3], [2|...]], [[3, 0], [3, 1], [3, 2], [3|...], [...|...]], [[4, 0], [4, 1], [4|...], [...|...]|...]] .

Anyone have any clue why this happens?

Thank you!

Answer 1

By default, the toplevel loop of SWI prints terms up to depth 10. Deeper parts are replaced by ... You can extend that depth or remove that limit by setting the depth to 0.

?- length(L,10).
L = [_G317, _G320, _G323, _G326, _G329, _G332, _G335, _G338, _G341|...].

?- current_prolog_flag(toplevel_print_options,V).
V = [quoted(true), portray(true), max_depth(10), spacing(next_argument)].

?- set_prolog_flag(toplevel_print_options, [quoted(true), portray(true), max_depth(0), spacing(next_argument)]).
true.

?- length(L,10).
L = [_G320, _G323, _G326, _G329, _G332, _G335, _G338, _G341, _G344, _G347].

— update: in newer versions of SWI, another flag must be changed:

?- current_prolog_flag(T,V), atom_concat(_,options,T).
T = answer_write_options,
V = [quoted(true), portray(true), max_depth(10), spacing(next_argument)] .

?- set_prolog_flag(answer_write_options, [quoted(true), portray(true), max_depth(0), spacing(next_argument)]).
true.