[Haskell-cafe] Re: Functors [Comments from OCaml Hacker Brian Hurt]

[Jonathan Cast]

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