progress towards saving export string in correct format (but note there is currently an exception somewhere because of changes; need to fix)

fcore/layer-tree.sml

@@ -46,6 +46,17 @@ struct
           foldl (f, right, acc)
         end
 
+  fun foldr (f, tree, acc) =
+    case tree of
+      LEAF => acc
+    | NODE {value, left, right, ...} =>
+        let
+          val acc = foldr (f, right, acc)
+          val acc = f (value, acc)
+        in
+          foldr (f, left, acc)
+        end
+
   fun map (f, tree) =
     case tree of
       LEAF => LEAF

fcore/parser/parser.md

@@ -16,6 +16,6 @@ layer ::= **[** item **]**
 layer_tree ::= int int **{** (layer)* **}**
 ```
 
-The first two `int`s in the grid `int int **{** (item)+ **}**` always follow the order: `canvasWidth canvasHeight`.
+The first two `int`s in the `layer_tree` always follow the order: `canvasWidth canvasHeight`.
 
-The large number of `int`s in the `item` always follows the order: `x y ex ey r g b a`.
+The large number of `int`s in the `item` always follow the order: `x y ex ey r g b a`.

fcore/quad-tree.sml

@@ -460,7 +460,7 @@ struct
   fun toSaveStringFolder ({x, ex, y, ey, data = {r, g, b, a}}, acc) =
     let
       val item = String.concat
-        [ "{"
+        [ "["
         , Int.toString x
         , " "
         , Int.toString y
@@ -476,20 +476,28 @@ struct
         , Int.toString b
         , " "
         , Int.toString a
-        , " } "
+        , " ] "
         ]
     in
       item :: acc
     end
 
-  fun toSaveString (squares, canvasWidth, canvasHeight) =
+  fun toSaveStringTreeFolder size (grid, acc) =
+    let
+      val qtree = buildTree (0, 0, size, grid)
+      val bintree = merge (qtree, grid)
+      val str = BinTree.foldr (toSaveStringFolder, bintree, [])
+    in
+      String.concat str :: acc
+    end
+
+  fun toSaveString (layerTree, canvasWidth, canvasHeight) =
     let
       val size = Int.max (canvasWidth, canvasHeight)
-      val qtree = buildTree (0, 0, size, squares)
-      val bintree = merge (qtree, squares)
+      val f = toSaveStringTreeFolder size
 
       val initial = ["}"]
-      val acc = BinTree.foldr (toSaveStringFolder, bintree, initial)
+      val acc = LayerTree.foldr (f, layerTree, initial)
       val acc =
         String.concat
           [Int.toString canvasWidth, " ", Int.toString canvasHeight, " { "]