fix bug with value inserted into ValSet: before, the value inserted into the 'from' field was the ID of the current platform, but this is incorrect as it is circular. To fix, the 'from' field now contains the ID of the previous platform which this platform was found from

fcore/bin-vec.sml

@@ -156,7 +156,7 @@ structure IntSet =
 structure ValSet =
   MakeBinVec
     (struct
-       type elem = {distance: int, from: char}
+       type elem = {distance: int, from: int}
 
        (* l, e and q functions are not actually used in the ValSet
        * because the IntSet is meant to contain keys while the ValSet

fcore/heap.sml

@@ -133,11 +133,11 @@ end
 structure DistHeap =
   MakeSkewHeap
     (struct
-       type t = {distance: int, id: int}
+       type t = {distance: int, id: int, comesFrom: int}
        type id = int
 
        (* default = defaultID returned when queue is empty *)
-       val default = {distance = ~1, id = ~1}
+       val default = {distance = ~1, id = ~1, comesFrom = ~1}
 
        fun getID {id, distance = _} = id
 

fcore/path-finding.sml

@@ -112,11 +112,9 @@ struct
                      if dist < oldDist then
                        (* update values as we found a shorter path *)
                        let
-                         val eVals = ValSet.updateAtIdx
-                           ( eVals
-                           , {distance = dist, from = Char.chr fromPlatID}
-                           , pos
-                           )
+                         val eVals =
+                           ValSet.updateAtIdx
+                             (eVals, {distance = dist, from = fromPlatID}, pos)
                        in
                          (eVals, q)
                        end
@@ -128,7 +126,13 @@ struct
                    (* key not explored, so add to queue *)
                    let
                      val q =
-                       DistHeap.insert ({distance = dist, id = foldPlatID}, q)
+                       DistHeap.insert
+                         ( { distance = dist
+                           , id = foldPlatID
+                           , comesFrom = fromPlatID
+                           }
+                         , q
+                         )
                    in
                      (eVals, q)
                    end
@@ -136,7 +140,14 @@ struct
              else
                (* key not explored, so add to queue *)
                let
-                 val q = DistHeap.insert ({distance = dist, id = foldPlatID}, q)
+                 val q =
+                   DistHeap.insert
+                     ( { distance = dist
+                       , id = foldPlatID
+                       , comesFrom = fromPlatID
+                       }
+                     , q
+                     )
                in
                  (eVals, q)
                end
@@ -251,10 +262,8 @@ struct
         val pos = IntSet.findInsPos (curID, eKeys)
 
         val {from, ...} = ValSet.sub (eVals, pos)
-        val from = Char.ord from
       in
-        if from = curID then acc
-        else helpGetPathList (from, eID, eKeys, eVals, acc)
+        helpGetPathList (from, eID, eKeys, eVals, acc)
       end
 
   fun getPathList (pID, eID, eKeys, eVals) =
@@ -271,7 +280,7 @@ struct
       else
         (* continue dijkstra's algorithm *)
         let
-          val {distance = distSoFar, id = minID} = DistHeap.findMin q
+          val {distance = distSoFar, id = minID, comesFrom} = DistHeap.findMin q
         in
           if minID = ~1 then
             (* return empty list to signify that there is no path *)
@@ -285,8 +294,9 @@ struct
               (* add explored *)
               val insPos = IntSet.findInsPos (minID, eKeys)
               val eKeys = IntSet.insert (eKeys, minID, insPos)
-              val eVals = ValSet.insert
-                (eVals, {distance = distSoFar, from = Char.chr minID}, insPos)
+              val eVals =
+                ValSet.insert
+                  (eVals, {distance = distSoFar, from = comesFrom}, insPos)
 
               val env =
                 { platforms = platforms
@@ -308,7 +318,7 @@ struct
               (* fold over quad tree, updating any distances 
                * we find the shortest path for *)
               val (eVals, q) = FindReachable.foldRegion
-                (x, y, width, height, 0, 0, ww, wh, env, state, platformTree)
+                (0, 0, ww, wh, 0, 0, ww, wh, env, state, platformTree)
             in
               loop (pID, eID, platforms, platformTree, q, eKeys, eVals)
             end
@@ -319,7 +329,7 @@ struct
     let
       (* initialise data structures: the priority queue and the explored map *)
       val q = DistHeap.empty
-      val q = DistHeap.insert ({distance = 0, id = eID}, q)
+      val q = DistHeap.insert ({distance = 0, id = eID, comesFrom = eID}, q)
 
       (* explored keys and values *)
       val eKeys = IntSet.empty