sudoku.pl

valid([]).
valid([Head|Tail]) :- 
  fd_all_different(Head), 
  valid(Tail).

sudoku(Puzzle, Solution) :- 
  Solution = Puzzle,
  Puzzle = [S11, S12, S13, S14,
			S21, S22, S23, S24,
			S31, S32, S33, S34,
			S41, S42, S43, S44], 
  fd_domain(Puzzle, 1, 4),
  
  Row1 = [S11, S12, S13, S14],
  Row2 = [S21, S22, S23, S24],
  Row3 = [S31, S32, S33, S34],
  Row4 = [S41, S42, S43, S44],
  
  Col1 = [S11, S21, S31, S41],
  Col2 = [S12, S22, S32, S42],
  Col3 = [S13, S23, S33, S43],
  Col4 = [S14, S24, S34, S44],
  
  Square1 = [S11, S12, S21, S22],
  Square2 = [S31, S32, S41, S42],
  Square3 = [S13, S14, S23, S24],
  Square4 = [S33, S34, S43, S44],

valid([Row1, Row2, Row3, Row4, Col1, Col2, Col3, Col4, Square1, Square2, Square3, Square4]).