add grid module, and change some functions in layer-tree.sml to use it instead of having grid-logic in there

dotscape.mlb

@@ -1,6 +1,7 @@
 $(SML_LIB)/basis/basis.mlb
 
 (* FUNCTIONAL CORE *)
+fcore/grid.sml
 fcore/layer-tree.sml
 fcore/app-type.sml
 

fcore/grid.sml

@@ -0,0 +1,23 @@
+structure Grid =
+struct
+  type square = {r: int, g: int, b: int, a: int}
+
+  type t = square vector vector
+
+  val emptyPixel = {r = 0, g = 0, b = 0, a = 0}
+
+  fun isBlank ({a, ...}: square) = a = 0
+
+  fun changeGridSize maxSide grid =
+    Vector.tabulate (maxSide, fn i =>
+      if i < Vector.length grid then
+        let
+          val yAxis = Vector.sub (grid, i)
+        in
+          Vector.tabulate (maxSide, fn ii =>
+            if ii < Vector.length yAxis then Vector.sub (yAxis, ii)
+            else emptyPixel)
+        end
+      else
+        Vector.tabulate (maxSide, fn _ => emptyPixel))
+end

fcore/layer-tree.sml

@@ -1,19 +1,11 @@
 structure LayerTree =
 struct
-  type square = {r: int, g: int, b: int, a: int}
-
-  type grid = square vector vector
-
   datatype tree =
-    NODE of {key: int, value: grid, left: tree, right: tree}
+    NODE of {key: int, value: Grid.t, left: tree, right: tree}
   | LEAF
 
-  val emptyPixel = {r = 0, g = 0, b = 0, a = 0}
-
   val emptyTree = LEAF
 
-  fun isBlank ({a, ...}: square) = a = 0
-
   fun insert (newKey, newValue, tree) =
     case tree of
       LEAF => NODE {key = newKey, value = newValue, left = LEAF, right = LEAF}
@@ -66,7 +58,7 @@ struct
       (fn (xIdx, valueYAxis) =>
          Vector.mapi
            (fn (yIdx, valuePixel) =>
-              if isBlank valuePixel then
+              if Grid.isBlank valuePixel then
                 let val accYAxis = Vector.sub (acc, xIdx)
                 in Vector.sub (accYAxis, yIdx)
                 end
@@ -75,26 +67,13 @@ struct
 
   fun makeEmptyGrid maxSide =
     Vector.tabulate (maxSide, fn _ =>
-      Vector.tabulate (maxSide, fn _ => emptyPixel))
+      Vector.tabulate (maxSide, fn _ => Grid.emptyPixel))
 
   fun flatten (maxSide, tree) =
     foldl (helpFlatten, tree, makeEmptyGrid maxSide)
 
-  fun helpChangeGridSize maxSide squares =
-    Vector.tabulate (maxSide, fn i =>
-      if i < Vector.length squares then
-        let
-          val yAxis = Vector.sub (squares, i)
-        in
-          Vector.tabulate (maxSide, fn ii =>
-            if ii < Vector.length yAxis then Vector.sub (yAxis, ii)
-            else emptyPixel)
-        end
-      else
-        Vector.tabulate (maxSide, fn _ => emptyPixel))
-
   fun changeGridSize (maxSide, tree) =
-    let val f = helpChangeGridSize maxSide
+    let val f = Grid.changeGridSize maxSide
     in map (f, tree)
     end
 end