slight renaming of constructors in FileMessage.t datatype, to provide more clarity (SAVE_TRIANGLES is for saving to a custom format, LOAD_TRIANGLES is for loading from a file in that custom format, and export is for generating code from custom format)

imperative-shell/file-thread.sml

@@ -12,8 +12,8 @@ struct
       val _ =
         case Mailbox.recv fileMailbox of
           SAVE_TRIANGLES triangles => ()
+        | LOAD_TRIANGLES triangles => ()
         | EXPORT_TRIANGLES triangles => ()
-        | IMPORT_TRIANGLES => ()
     in
       run fileMailbox
     end