declare
% Returns the list of solutions of Script given by a lazy
% depth-first exploration
fun {Solve Script}
   {SolveStep {Space.new Script} nil}
end

% Returns the list of solutions of S appended with SolTail
fun {SolveStep S SolTail}
   case {Space.ask S}
   of failed          then SolTail
   [] succeeded       then {Space.merge S}|SolTail
   [] alternatives(N) then {SolveLoop S 1 N SolTail}
   end
end

% Lazily explores the alternatives I through N of space S,
% and returns the list of solutions found, appended with
% SolTail
fun lazy {SolveLoop S I N SolTail}
   if I>N then
      SolTail
   elseif I==N then
      {Space.commit S I}
      {SolveStep S SolTail}
   else
      C={Space.clone S}
      NewTail={SolveLoop S I+1 N SolTail}
   in
      {Space.commit C I}
      {SolveStep C NewTail}
   end
end