18 Jan
2009
18 Jan
'09
12:50 p.m.
On Sun, 2009-01-18 at 11:11 +0000, Andrew Coppin wrote:
Heinrich Apfelmus wrote:
Andrew Coppin wrote:
instance (Monad m) => Functor m where fmap f ma = do a <- ma; return (f a)
While that's quite interesting from a mathematical point of view, how is this "useful" for programming purposes?
Surely, you agree that liftM is "useful"? Because that's the same thing.
Then why not just use liftM? (That way, you know what it does...)
I'd be willing to say *you* don't `know what it does', if you haven't figured out that it's an acceptable implementation of fmap first. jcc