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Matt Harden
"Manuel M. T. Chakravarty" wrote:
* I am not a big fan of introducing an extra monad (`GUI' in this case). It can easily become a pain in programs that do a lot of "normal" IO as you have to lift all IO functions to GUI.
Shouldn't GUI be a typeclass (as a subclass of Monad), with IO being an instance of it? This gives the following benefits:
o "Pure" GUI functions can reflect this in their type. i.e. (GUI g) => g () o IO functions can use GUI features directly without lifting. o "Pure" GUI functions are implicitly usable in the IO monad They "are" IO functions.
That's an interesting idea. The main problem that I am seeing at the moment is that the basic GUI functionality that usually is imported from C libraries via the FFI will be in IO. That's because foreign imports of sideeffecting functions (which almost all basic GUI functions are) are required to be of type `a -> IO b'. This constraints the GUI monad to be IO or an extension of IO; unless you want to get into some rather ugly messing around with `unsafePerformIO'. Cheers, Manuel