%-----------------------------------------------------------
% Inefficient breadth-first search (nearly identical to depth-first search)
%-----------------------------------------------------------
breadth_first_search_slow(Arc,Start,GoalPred,Sol):-
  bfs_slow(Arc,[[Start]],[],GoalPred,Sol).

bfs_slow(_,[[Node|Path]|_],_,GoalPred,[Node|Path]):-
   call(GoalPred,Node).

bfs_slow(Arc,[[Node|Path]|MoreOPEN],CLOSED,GoalPred,Sol):-
  findall([Next,Node|Path],
  (call(Arc,Node,Next),
   not(member([Next|_],[[Node|Path]|MoreOPEN])),
   not(member(Next,CLOSED))),
  NewPaths),
  % place the new paths on the bottom of the queue
  append(MoreOPEN,NewPaths,NewOPEN),
  %closing(Node),
  bfs_slow(Arc,NewOPEN,[Node|CLOSED],GoalPred,Sol).