lib/astar: fix return value for failed search

lib/astar.py

@@ -4,7 +4,6 @@ def search(start, is_goal, neighbors, heuristic=None):
     if heuristic == None:
         def heuristic(x):
             return 0
-    # TODO: callable goal
     if not callable(is_goal):
         goal = is_goal
         def is_goal(this):
@@ -44,7 +43,7 @@ def search(start, is_goal, neighbors, heuristic=None):
                 i += 1
                 heappush(q, (c, i, n, this))
 
-    return float('inf'), None
+    return float('inf'), None, []
 
 def test():
     data = [