Dougal Stanton wrote:
Is there some sort of equivalent of the if/then/else construct for use in the IO monad? For instance the following can get quite tedious:
do bool <- doesFileExist filename if bool then sth else sth'
Is there a more compact way of writing that? Something akin to:
condM (doesFileExist filename) (sth) (sth')
Or maybe there's a more sensible way of doing the above that I've missed. I seem to use endless alternate conditions sometimes and there's bound to be a better way.
I don't know any existing function like this in the current libs. Here i paste probably a possible implementation for one. if' :: (Monad m) => m Bool -> m b -> m b -> m b if' mb mt mf = mb >>= if'' where if'' b = if b then mt else mf Regards,