"Nicola Paolucci" <[EMAIL PROTECTED]> writes: > Hi All, > > I'm loving learning Haskell quite a bit. > It is stretching my brain but in a delightfull way. > > I've googled, I've hoogled but I haven't found a clear explanation for > what exactly liftM2 does in the context below. > > Using the cool lambdabot "pointless" utility I found out that: > > > \x -> snd(x) - fst(x) > > is the same as: > > > liftM2 (-) snd fst > > I like the elegance of this but I cannot reconcile it with its type. I > can't understand it. > I check the signature of liftM2 and I get: > > Prelude> :t liftM2 > Prelude> liftM2 :: (Monad m) => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r > > Can someone help me understand what's happening here ? > What does a Monad have to do with a simple subtraction ? > What is actually the "m" of my example ? > > I am sure if I get this I'll be another step closer to illumination ...
Does typing :t liftM2 (-) snd into ghc enlighten you at all? -- Jón Fairbairn [EMAIL PROTECTED] _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
