keep track of visited nodes to prevent infinite recursion

fcore/enemy-behaviour.sml

@@ -132,17 +132,32 @@ struct
     end
 
   (* new pathfinding using quad tree *)
+  fun helpHasVisited (pos, find, visited) =
+    if pos = Vector.length visited then
+      false
+    else
+      let val cur = Vector.sub (visited, pos)
+      in cur = find orelse helpHasVisited (pos + 1, find, visited)
+      end
+
+  fun hasVisted (find, visited) =
+    helpHasVisited (0, Char.chr find, visited)
+
   fun getUpwardsPath
-    (playerPlatID, currentPlatID, platforms, platformTree, dist) =
+    (playerPlatID, currentPlatID, platforms, platformTree, dist, visited) =
     if playerPlatID = currentPlatID then
       (dist, [currentPlatID])
     else
       let
+        (* add current node to list of visited nodes *)
+        val chr = Char.chr currentPlatID
+        val visited = Vector.concat [Vector.fromList [chr], visited]
+
         val currentPlat = Platform.find (currentPlatID, platforms)
         val {x, y, width, ...} = currentPlat
 
-        val searchY = y - Constants.jumpLimit - 1
+        val searchY = y - Constants.jumpLimit
-        val searchH = Constants.jumpLimit
+        val searchH = Constants.jumpLimit + 1
 
         (* todo: x/width are placeholder values.
          * They should define values that let reachable platforms 
@@ -166,6 +181,7 @@ struct
           , currentPlat
           , ~1
           , []
+          , visited
           )
       in
         if bestDist = ~1 then
@@ -185,9 +201,23 @@ struct
     , prevPlat
     , bestDist
     , bestPath
+    , visited
     ) =
     case lst of
       id :: tl =>
+        if hasVisted (id, visited) then
+          helpGetUpwardsPath
+            ( playerPlatID
+            , platforms
+            , platformTree
+            , tl
+            , dist
+            , prevPlat
+            , bestDist
+            , bestPath
+            , visited
+            )
+        else
           let
             val currentPlat = Platform.find (id, platforms)
             val {y = cy, ...} = currentPlat
@@ -197,7 +227,7 @@ struct
             val platDist = dist + diff
 
             val (newDist, newPath) = getUpwardsPath
-            (playerPlatID, id, platforms, platformTree, platDist)
+              (playerPlatID, id, platforms, platformTree, platDist, visited)
           in
             if newDist = ~1 then
               (* newPath is invalid, so reuse old path *)
@@ -210,6 +240,7 @@ struct
                 , prevPlat
                 , bestDist
                 , bestPath
+                , visited
                 )
             else if bestDist = ~1 then
               (* bestPath is invalid *)
@@ -222,6 +253,7 @@ struct
                 , prevPlat
                 , newDist
                 , newPath
+                , visited
                 )
             else if newDist < bestDist then
               helpGetUpwardsPath
@@ -233,6 +265,7 @@ struct
                 , prevPlat
                 , newDist
                 , newPath
+                , visited
                 )
             else
               helpGetUpwardsPath
@@ -244,6 +277,7 @@ struct
                 , prevPlat
                 , bestDist
                 , bestPath
+                , visited
                 )
           end
     | [] => (bestDist, bestPath)
@@ -309,7 +343,7 @@ struct
 
       val (bestDist, bestPath) =
         if eID > ~1 andalso pID > ~1 then
-          getUpwardsPath (pID, eID, platforms, platformTree, 0)
+          getUpwardsPath (pID, eID, platforms, platformTree, 0, "")
         else
           (~1, [])