Sudoku Solver in Prolog

sudoku.pl

squares([
          [X11, X12, X13, X14, X15, X16, X17, X18, X19],
          [X21, X22, X23, X24, X25, X26, X27, X28, X29],
          [X31, X32, X33, X34, X35, X36, X37, X38, X39],
          [X41, X42, X43, X44, X45, X46, X47, X48, X49],
          [X51, X52, X53, X54, X55, X56, X57, X58, X59],
          [X61, X62, X63, X64, X65, X66, X67, X68, X69],
          [X71, X72, X73, X74, X75, X76, X77, X78, X79],
          [X81, X82, X83, X84, X85, X86, X87, X88, X89],
          [X91, X92, X93, X94, X95, X96, X97, X98, X99]
        ],
        [
          [X11, X12, X13, X21, X22, X23, X31, X32, X33],
          [X41, X42, X43, X51, X52, X53, X61, X62, X63],
          [X71, X72, X73, X81, X82, X83, X91, X92, X93],
          [X14, X15, X16, X24, X25, X26, X34, X35, X36],
          [X44, X45, X46, X54, X55, X56, X64, X65, X66],
          [X74, X75, X76, X84, X85, X86, X94, X95, X96],
          [X17, X18, X19, X27, X28, X29, X37, X38, X39],
          [X47, X48, X49, X57, X58, X59, X67, X68, X69],
          [X77, X78, X79, X87, X88, X89, X97, X98, X99]
        ]).

transpose([[A]],[[A]]).
transpose([[A|H]|T],[[A|HH]|TT]):-
   set_heads(T,HH,R),
   set_heads(TT,H,RR),
   transpose(R,RR).

set_heads([],[],[]).
set_heads([[H|T]|L],[H|TT],[T|R]):-
   set_heads(L,TT,R).

all_different_list([]).
all_different_list([H|T]) :-
  fd_all_different(H),
  all_different_list(T).

domain(1).
domain(2).
domain(3).
domain(4).
domain(5).
domain(6).
domain(7).
domain(8).
domain(9).

domain_array([]).
domain_array([H|T]) :-
  domain(H),
  domain_array(T).

domain_matrix([]).
domain_matrix([H|T]) :-
  domain_array(H),
  domain_matrix(T).

sudoku(Rows) :-
  domain_matrix(Rows),

  transpose(Rows, Columns),
  squares(Rows, Squares),

  all_different_list(Rows),
  all_different_list(Columns),
  all_different_list(Squares).

test1 :-
  L = [
         [_,6,_,1,_,4,_,5,_],
         [_,_,8,3,_,5,6,_,_],
         [2,_,_,_,_,_,_,_,1],
         [8,_,_,4,_,7,_,_,6],
         [_,_,6,_,_,_,3,_,_],
         [7,_,_,9,_,1,_,_,4],
         [5,_,_,_,_,_,_,_,2],
         [_,_,7,2,_,6,9,_,_],
         [_,4,_,5,_,8,_,7,_]
  ],
  sudoku(L),
  pp(L).


test3 :-
  L = [
        [_,4,3,_,8,_,2,5,_],
        [6,_,_,_,_,_,_,_,_],
        [_,_,_,_,_,1,_,9,4],
        [9,_,_,_,_,4,_,7,_],
        [_,_,_,6,_,8,_,_,_],
        [_,1,_,2,_,_,_,_,3],
        [8,2,_,5,_,_,_,_,_],
        [_,_,_,_,_,_,_,_,5],
        [_,3,4,_,9,_,7,1,_]
  ],
  sudoku(L),
  pp(L).


test5 :-
  L = [
        [_,_,_,1,5,_,_,7,_],
        [1,_,6,_,_,_,8,2,_],
        [3,_,_,8,6,_,_,4,_],
        [9,_,_,4,_,_,5,6,7],
        [_,_,4,7,_,8,3,_,_],
        [7,3,2,_,_,6,_,_,4],
        [_,4,_,_,8,1,_,_,9],
        [_,1,7,_,_,_,2,_,8],
        [_,5,_,_,3,7,_,_,_]
  ],
  sudoku(L),
  pp(L).

testHard :-
  L = [
      [1, _, _,  _, _, 7,  _, 9, _],
      [_, 3, _,  _, 2, _,  _, _, 8],
      [_, _, 9,  6, _, _,  5, _, _],
      %%%%%%%%%  %%%%%%%%  %%%%%%%%%
      [_, _, 5,  3, _, _,  9, _, _],
      [_, 1, _,  _, 8, _,  _, _, 2],
      [6, _, _,  _, _, 4,  _, _, _],
      %%%%%%%%%  %%%%%%%%  %%%%%%%%%
      [3, _, _,  _, _, _,  _, 1, _],
      [_, 4, _,  _, _, _,  _, _, 7],
      [_, _, 7,  _, _, _,  3, _, _]
  ],
  sudoku(L),
  pp(L).

pp([]).
pp([H|T]) :-
  write(H),nl,
  pp(T).

como hago la consulta??

please provide video for detail explanation