--- Glynn Clements
3. Personally, I would prefer a generic widget creation function, rather than a different function for each type of widget. E.g. Xt has XtCreateWidget(), with the widget class being passed as an argument. A more Haskell-ish approach would be to use typeclasses, e.g.:
class Widget a where create :: String -> a -> [Property] -> IO a -- create name parent properties = ...
That should be:
create :: (Widget b) => String -> b -> [Property] -> IO a
A widget's parent must be a widget, but not necessarily the same type of widget.
Ahh, I thought you wanted to create widgets based on the String parameter. So in the following code, you would get an ambiguity error, right? do -- mainWindow defined above a <- create "Some_Button" mainWindow [ label := "Okay" ] runGUI mainWindow -- or whatever it is. The system does not know if a is a button, a label, or whatever. It would have to look like this to remove the ambiguity do -- mainWindow defined above a <- create "Some_Button" mainWindow [ label := "Okay" ] :: Button runGUI mainWindow -- or whatever it is. It seems like this would defeat the purpose of having a generic create function since Button needs to be in there somewhere. Although, I do find your argument very credible. David J. Sankel