On Fri, Feb 13, 2009 at 05:21:50PM +0100, Thomas Davie wrote:
Hey,
Thanks for all the suggestions. I was hoping that there was some uniform pattern that would extend to n arguments (rather than having to use liftM2, litM3, etc. or have different 'application' operators in between the different arguments); perhaps not. Oh well :)
Sure you can! What you want is Control.Applicative, not Control.Monad.
(<*>) is the generic application you're looking for:
pure (+) <*> [1,2,3] <*> [4,5,6] [5,6,7,6,7,8,7,8,9]
Note that pure f <*> y can be shortened to fmap though, which Control.Applicative defines a handy infix version of:
(+) <$> [1,2,3] <*> [4,5,6] [5,6,7,6,7,8,7,8,9]
Hope that provides what you want
Hi Bob, Thanks for the suggestion, but that solution does not work when the function I want to apply (in your case, +) is monadic itself. Then I'd still have to write join $ f <*> [1,2,3] <*> [4,5,6] :( Edsko