write code for new loop implementation of dijkstra's algorithm, which uses a precomputed graphy; however, this is not used yet as we need to add the graph to the game type first, and pass it along with other parameters, down to the path-finding.sml function

fcore/path-finding.sml

@@ -35,6 +35,69 @@ struct
   fun getPathList (pID, eID, eKeys, eVals) =
     helpGetPathList (pID, eID, eKeys, eVals, [])
 
+  fun helpExplore (pos, graphNode, minID, distSoFar, q) =
+    if pos = Vector.length graphNode then
+      q
+    else
+      let
+        val {distance = newPlatDist, id = newPlatID} =
+          Vector.sub (graphNode, pos)
+
+        val totalDist = newPlatDist + distSoFar
+
+        val insRecord =
+          {distance = totalDist, id = newPlatID, comesFrom = minID}
+        val insPos = DistVec.findInsPos (insRecord, q)
+        val q = DistVec.insert (q, insRecord, insPos)
+      in
+        helpExplore (pos + 1, graphNode, minID, distSoFar, q)
+      end
+
+  fun explore (graphNode, minID, distSoFar, q) =
+    helpExplore (0, graphNode, minID, distSoFar, q)
+
+  fun loop (pID, eID, platforms, platformTree, q, eKeys, eVals, graph) =
+    if IntSet.contains (pID, eKeys) then
+      (* return path if we explored pid *)
+      getPathList (pID, eID, eKeys, eVals)
+    else
+      (* continue dijkstra's algorithm *)
+      let
+        (* filtering duplicates because we have no decrease-key operation *)
+        val q = filterMinDuplicates (q, eKeys)
+      in
+        if DistVec.isEmpty q then
+          (* return empty list to signify that there is no path *)
+          []
+        else
+          (* find reachable values from min in quad tree *)
+          let
+            val {distance = distSoFar, id = minID, comesFrom} =
+              DistVec.findMin q
+
+            (* explore platforms connected to minID *)
+            val platPos = Platform.findPos (minID, platforms)
+            val plat = Vector.sub (platforms, platPos)
+            val graphNode = Vector.sub (graph, platPos)
+
+            (* on each loop, increment distSoFar by 15.
+             * Result: paths that require jumps to fewer platforms are
+             * incentivised a little bit. *)
+            val q = explore (graphNode, minID, distSoFar + 15, q)
+
+            (* mark platform with (id = minID) as explored *)
+            val insPos = IntSet.findInsPos (minID, eKeys)
+            val eKeys = IntSet.insert (eKeys, minID, insPos)
+            val eVals =
+              ValSet.insert
+                (eVals, {distance = distSoFar, from = comesFrom}, insPos)
+          in
+            loop (pID, eID, platforms, platformTree, q, eKeys, eVals, graph)
+          end
+      end
+
+  (* dead loop function: remove after adding graph to game type 
+   * and moving to other loop *)
   fun loop (pID, eID, platforms, platformTree, q, eKeys, eVals) =
     if IntSet.contains (pID, eKeys) then
       (* return path if we explored pid *)

fcore/platform.sml

@@ -23,19 +23,24 @@ struct
       , QuadTree.create (Constants.worldWidth, Constants.worldHeight)
       )
 
-  fun helpFind (findNum, vec, low, high) =
+  fun helpFindPos (findNum, vec, low, high) =
     let
       val mid = low + ((high - low) div 2)
       val platform = Vector.sub (vec, mid)
       val {id = curNum, x = _, y = _, width = _} = platform
     in
-      if curNum = findNum then platform
-      else if curNum < findNum then helpFind (findNum, vec, mid + 1, high)
-      else helpFind (findNum, vec, low, mid - 1)
+      if curNum = findNum then mid
+      else if curNum < findNum then helpFindPos (findNum, vec, mid + 1, high)
+      else helpFindPos (findNum, vec, low, mid - 1)
     end
 
+  fun findPos (findNum, vec) =
+    helpFindPos (findNum, vec, 0, Vector.length vec - 1)
+
   fun find (findNum, vec) =
-    helpFind (findNum, vec, 0, Vector.length vec - 1)
+    let val pos = findPos (findNum, vec)
+    in Vector.sub (vec, pos)
+    end
 
   fun helpGetDrawVecWider
     (pos, platVec, acc, winWidth, winHeight, ratio, yOffset) =