Am Freitag 17 April 2009 01:37:25 schrieb Tsunkiet Man:
Hello,
what you suggested worked! Im very happy with it. However another error suddenly came up. It sais the last statement in a 'do' must be an expression, he is refering to line 41:45
I change my code to this:
on (menu exit) := close f, on (menu open) := onOpen f dt vFile ]
return ()
where onOpen :: Frame a -> staticText c -> Var b -> IO () onOpen frame stat var = do file <- fileOpenDialog frame False True "Open File" [("PGM bestanden (*.pgm)",["*.pgm"]),("Alle bestanden (*.*)",["*.*"])] "" "" case file of Nothing -> return () Just file -> set stat [text
:= "HELLO"]
return ()
In the "Just file" case, you want to have two IO-actions. If you don't use (>>=) or (>>) to chain them together, you must put them in a do-block, so case file of Nothing -> return () Just file -> do set stat [text := "HELLO"] return () But I think you can omit the return () in that branch anyway, set foo bar should have the correct type already.
As far as I can tell, if the file is nothing it will return something of IO () and if the file is something it will return something of IO (). So that error is kind of strange in my opinion. Do you know what caused it?
Thanks for your help!