fix lexer/parser bugs, add code in file-thread.sml to handle loading/saving of files (but loading is not completely finished yet)

imperative-shell/file-thread.sml

@@ -8,8 +8,6 @@ struct
   open FileMessage
   open InputMessage
 
-  datatype parse_result = OK of unit | PARSE_ERROR
-
   val structureName = "Green"
   val filename = "green.dsc"
   val exportFilename = "green.sml"
@@ -49,7 +47,21 @@ struct
 
   fun parse (io, acc) = ()
 
-  fun loadSquares (path, inputMailbox) = ()
+  fun loadIO (io, str) =
+    case TextIO.inputLine io of
+      SOME line => loadIO (io, str ^ line)
+    | NONE => str
+
+  fun loadSquares (path, inputMailbox) =
+    let
+      val io = TextIO.openIn filename
+      val str = loadIO (io, "")
+      val () = TextIO.closeIn io
+    in
+      case Parser.parse str of
+        SOME (canvasWidth, canvasHeight, grid) => ()
+      | NONE => ()
+    end
 
   fun saveSquares squaresString =
     let