Prolog returning false for sudoku solver - prolog

Question

:-use_module(library(clpfd)).
solve(X,Board):-
Board=X,
Board =
[A1,A2,A3,A4,A5,A6,A7,A8,A9,
B1,B2,B3,B4,B5,B6,B7,B8,B9,
C1,C2,C3,C4,C5,C6,C7,C8,C9,
D1,D2,D3,D4,D5,D6,D7,D8,D9,
E1,E2,E3,E4,E5,E6,E7,E8,E9,
F1,F2,F3,F4,F5,F6,F7,F8,F9,
G1,G2,G3,G4,G5,G6,G7,G8,G9,
H1,H2,H3,H4,H5,H6,H7,H8,H9,
I1,I2,I3,I4,I5,I6,I7,I8,I9],
Board ins 1..9,
label(Board),
%rows on the board
all_different([A1,A2,A3,A4,A5,A6,A7,A8,A9]),
all_different([B1,B2,B3,B4,B5,B6,B7,B8,B9]),
all_different([C1,C2,C3,C4,C5,C6,C7,C8,C9]),
all_different([D1,D2,D3,D4,D5,D6,D7,D8,D9]),
all_different([E1,E2,E3,E4,E5,E6,E7,E8,E9]),
all_different([F1,F2,F3,F4,F5,F6,F7,F8,F9]),
all_different([G1,G2,G3,G4,G5,G6,G7,G8,G9]),
all_different([H1,H2,H3,H4,H5,H6,H7,H8,H9]),
all_different([I1,I2,I3,I4,I5,I6,I7,I8,I9]),
%columns on the board
all_different([A1,B1,C1,D1,E1,F1,G1,H1,I1]),
all_different([A2,B2,C2,D2,E2,F2,G2,H2,I2]),
all_different([A3,B3,C3,D3,E3,F3,G3,H3,I3]),
all_different([A4,B4,C4,D4,E4,F4,G4,H4,I4]),
all_different([A5,B5,C5,D5,E5,F5,G5,H5,I5]),
all_different([A6,B6,C6,D6,E6,F6,G6,H6,I6]),
all_different([A7,B7,C7,D7,E7,F7,G7,H7,I7]),
all_different([A8,B8,C8,D8,E8,F8,G8,H8,I8]),
all_different([A9,B9,C9,D9,E9,F9,G9,H9,I9]),
%different boxes
all_different([A1,A2,A3,B1,B2,B3,C1,C2,C3]),
all_different([A4,A5,A6,B4,B5,B6,C4,C5,C6]),
all_different([A7,A8,A9,B7,B8,B9,C7,C8,C9]),
all_different([D1,D2,D3,E1,E2,E3,F1,F2,F3]),
all_different([D4,D5,D6,E4,E5,E6,F4,F5,F6]),
all_different([D7,D8,D9,E7,E8,E9,F7,F8,F9]),
all_different([G1,G2,G3,H1,H2,H3,I1,I2,I3]),
all_different([G4,G5,G6,H4,H5,H6,I4,I5,I6]),
all_different([G7,G8,G9,H7,H8,H9,I7,I8,I9]).
37 ?- solve(Solution,[,,,,,,,,,,,,,,3,,8,5,,,1,,2,,,,,,,,5,,7,,,,,,,5,,7,,,,,,4,,,,1,,,,9,,,,,,,,5,,,,,,,7,3,,,2,,1,,,,,,,,,4,,,_,9]).
false.
Well, below there's a hyperlink of code to compare mine to, I compared it myself and apart from the fact that mine's 9x9 and his is 4x4 (and that I use ins instead of fd_domain) I can see no difference...My question is, might this be false because I'm using ins instead of fd_domain or is it something else that I can't see?
Some code which I compared my own to

Answer 1

Normally, label/1 it's called after all constraint posting. That's because it must, well, label each variable, i.e. enumerate remaining values after pruning. But your main problem it's that you're passing a wrong board, of 90 elements, instead of 81, as it should be.
I can show you with this weird 'query':
?- atomic_list_concat(L, ',', ',,,,,_,,,_,,,_,,,3,,8,5,,_,1,,2,,_,,,_,,,5,,7,,_,,,_,,5,,7,,,_,,,4,,,_,1,,,_,9,,,_,,,_,,5,,_,,,_,,7,3,,_,2,,1,,_,,,_,,,_,4,,,_,9'),findall(Y,(between(1,10,_),length(Y,9)),G), append(G,L),maplist(writeln,G).
[,,,,,_,,,_]
[,,_,,,3,,8,5]
[,_,1,,2,,_,,]
[_,,,5,,7,,_,]
[,_,,5,,7,,,_]
[,,4,,,_,1,,]
[_,9,,,_,,,_,]
[5,,_,,,_,,7,3]
[,_,2,,1,,_,,]
[_,,,_,4,,,_,9]
L = ['', '', '', '', '', '_', '', '', '_'|...],
G = [['', '', '', '', '', '_', '', ''|...], ['', '', '_', '', '', '3', ''|...], ['', '_', '1', '', '2', ''|...], ['_', '', '', '5', ''|...], ['', '_', '', '5'|...], ['', '', '4'|...], ['_', '9'|...], ['5'|...], [...|...]|...].
try to call your program in this way (just a sample, to show a proper fomatting):
?- solve([
/* 1,2,3,4,5,6,7,8,9 */
_,_,2,_,_,_,_,_,_,
1,_,_,_,8,_,_,_,_,
...
/* there must be 9 rows */
], X).