%%%For 8X8 chessboard with N queens.
-module(queens).
-export([queens/1]).

queens(0) -> [[]];
queens(N) ->
     [[Row | Columns] || Columns <- queens(N-1),
          Row <- [1,2,3,4,5,6,7,8] -- Columns,
          safe(Row, Columns, 1)].

safe(_Row, [], _N) -> true;
safe(Row, [Column|Columns], N) ->
     (Row /= Column + N) andalso (Row /= Column - N) andalso
          safe(Row, Columns, (N+1)).