I suspect get is provided by GtkHS and runs in the IO monad... try this this
sz <- get sizeBox entryText
let size = (read sz) :: Int
On 11 October 2010 17:19, Tom Hobbs
Hi all,
I playing around with simple cell automaton (Conway's Game Of Life). I've got working code which prints everything out nicely to the terminal, I'm trying to wrap everything in a nice GUI using Glade and Gtk2Hs.
In order to create my world, I have a function defined as;
makeWorld :: Int -> [(Int,Int)]
Which accepts an Int, representing the size of the world, then then outs the world itself - note the world is always assumed to be square. The list contains pairs such that the first element of the pair is the index (such as for an array) and the second is the value at that position. For right or wrong, that's how my (working) Game Of Life has been implemented. The problem comes in the Gtk2Hs code...
main = do initGUI Just xml <- xmlNew "gameOfLife.glade" window <- xmlGetWidget xml castToWindow "mainWindow" onDestroy window mainQuit quitButton <- xmlGetWidget xml castToButton "quitButton" onClicked quitButton $ do widgetDestroy window setWorldSize <- xmlGetWidget xml castToButton "setWorldSize" sizeBox <- xmlGetWidget xml castToEntry "worldSize" onClicked setWorldSize $ do canvas <- xmlGetWidget xml castToDrawingArea "world" let size = (read (get sizeBox entryText) :: Int) cellworld <- makeWorld size printWorld cellworld widgetShowAll window mainGUI
The above function does not compile under GHC because;
gameOfLife.hs:27:20: Couldn't match expected type `String' against inferred type `IO String' In the first argument of `read', namely `(get sizeBox entryText)' In the expression: (read (get sizeBox entryText) :: Int) In the definition of `size': size = (read (get sizeBox entryText) :: Int)
gameOfLife.hs:28:2: Couldn't match expected type `[(Int, Int)]' against inferred type `IO (Int, Int)' In a stmt of a 'do' expression: cellworld <- makeWorld size In the second argument of `($)', namely `do { canvas <- xmlGetWidget xml castToDrawingArea "world"; let size = (read (get sizeBox entryText) :: Int); cellworld <- makeWorld size; printWorld cellworld }' In a stmt of a 'do' expression: onClicked setWorldSize $ do { canvas <- xmlGetWidget xml castToDrawingArea "world"; let size = (read (get sizeBox entryText) :: Int); cellworld <- makeWorld size; printWorld cellworld }
It seems to be complaining about the call to my makeWorld function, although I do not understand why that should be. The line number which GHC complains about does correspond to the "cellworld <- makeWorld size" line in my main function.
I've not yet worked out how to draw my world in the GUI, the "printWorld" function mentioned above just spills the world out to the termainal for now.
Does anyone have any ideas?
Many thanks,
Tom _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners