begin parser to load from file

fcore/app-with.sml

@@ -3,12 +3,12 @@ struct
   open AppType
 
   fun updateSquares (squares, newX, newY, item) =
-    Vector.mapi
-      (fn (idx, el) =>
-         if idx = newX then
-           Vector.mapi (fn (iidx, iel) => if iidx = newY then item else iel) el
-         else
-           el) squares
+  let
+    val yAxis = Vector.sub (squares, newX)
+    val yAxis = Vector.update (yAxis, newY, item)
+  in
+    Vector.update (squares, newX, yAxis)
+  end
 
   fun changeSquaresSize (squares, newCanvasWidth, newCanvasHeight) =
     let