add function in imperative shell to save export string, and fix errors in generating export string from functional core

fcore/quad-tree.sml

@@ -525,7 +525,7 @@ struct
       val b = colToRealString b
 
       val x = String.concat ["(((x + ", x, ") - halfWidth) / halfWidth)"]
-      val y = String.concat ["(~(y + ", y, ") - halfHeight) / halfHeight)"]
+      val y = String.concat ["((~(y + ", y, ") - halfHeight) / halfHeight)"]
 
       val ex = String.concat
         [ "((((("
@@ -570,7 +570,7 @@ struct
       val bintree = merge (qtree, squares)
 
       val coords = BinTree.foldr (toExportStringFolder, bintree, [])
-      val coords = String.concatWith "," coords
+      val coords = String.concatWith ",\n" coords
 
       val header = String.concat
         [ "structure AAA = \nstruct\n"
@@ -582,7 +582,7 @@ struct
         , "     #[\n"
         ]
 
-      val footer = String.concat ["      ]\n", "    end\n", "end\n"]
+      val footer = String.concat ["\n      ]\n", "    end\n", "end\n"]
     in
       String.concat [header, coords, footer]
     end

imperative-shell/file-thread.sml

@@ -12,41 +12,6 @@ struct
   val filename = "green.dsc"
   val exportFilename = "green.sml"
 
-  fun ndcToLerpX num =
-    let
-      val num = (num + 1.0) / 2.0
-      val num = Real32.toString num
-      val num =
-        (* Problem: It seems that Real32.toString may sometimes return a string
-         * that is recognised as an integer, like "1" instead of "1.0".
-         * If that happens, we just add a ".0" to the end 
-         * so it's recognised as a real. *)
-        if String.isSubstring "." num then num
-        else num ^ ".0"
-    in
-      "      (((startX * (1.0 - " ^ num ^ ")) + (endX * " ^ num
-      ^ ")) / windowWidth) - 1.0"
-    end
-
-  fun ndcToLerpY num =
-    let
-      val num = (num + 1.0) / 2.0
-      val num = Real32.toString num
-      val num = if String.isSubstring "." num then num else num ^ ".0"
-    in
-      "      (((startY * (1.0 - " ^ num ^ ")) + (endY * " ^ num
-      ^ ")) / windowHeight) - 1.0"
-    end
-
-  fun colToString col =
-    let val col = Real32.toString col
-    in if String.isSubstring "." col then col else col ^ ".0"
-    end
-
-  fun exportSquares squares = ()
-
-  fun parse (io, acc) = ()
-
   fun loadIO (io, str) =
     case TextIO.inputLine io of
       SOME line => loadIO (io, str ^ line)
@@ -76,6 +41,14 @@ struct
       TextIO.closeOut io
     end
 
+  fun exportSquares squaresString =
+    let
+      val io = TextIO.openOut exportFilename
+      val () = TextIO.output (io, squaresString)
+    in
+      TextIO.closeOut io
+    end
+
   fun getDirList (dir, acc, rootPath) =
     case OS.FileSys.readDir dir of
       SOME path =>
@@ -112,7 +85,7 @@ struct
         case Mailbox.recv fileMailbox of
           SAVE_SQUARES str => saveSquares str
         | LOAD_SQUARES => loadSquares (filename, inputMailbox)
-        | EXPORT_SQUARES triangles => exportSquares triangles
+        | EXPORT_SQUARES str => exportSquares str
         | LOAD_FILES path => loadFiles (path, inputMailbox)
         | SELECT_PATH path => selectPath (path, inputMailbox)
     in