add function to quad tree to turn items into strings (for later saving to file)

fcore/parser/parse-grid.sml

@@ -0,0 +1,35 @@
+structure ParseGrid =
+struct
+  fun make (canvasWidth, canvasHeight) =
+    let
+      val maxPoints = Int.max (canvasWidth, canvasHeight)
+      val emptyYAxis = Vector.tabulate (maxPoints, fn _ => {r = 0, g = 0, b = 0, a = 0})
+    in
+      Vector.tabulate (maxPoints, fn _ => emptyYAxis)
+    end
+
+  local
+    fun loopY (yAxis, x, ex, y, ey, colour) =
+      if y > ey then yAxis
+      else
+        let
+          val yAxis = Vector.update (yAxis, y, colour)
+        in
+          loopY (yAxis, x, ex, y + 1, ey, colour)
+        end
+
+    fun loopX (grid, x, ex, y, ey, colour) =
+      if x > ex then grid
+      else
+        let
+          val yAxis = Vector.sub (grid, x)
+          val yAxis = loopY (yAxis, x, ex, y, ey, colour)
+          val grid = Vector.update (grid, x, yAxis)
+        in
+          loopX (grid, x + 1, ex, y, ey, colour)
+        end
+  in
+    fun applyItem (grid, x, y, ex, ey, colour) =
+      loopX (grid, x, ex, y, ey, colour)
+  end
+end