On Thu, Dec 22, 2005 at 02:02:56PM +0000, Daniel Carrera wrote: > Paul Moore wrote: > >As I say, I'm not trying to criticize anyone here, but it seems to be > >quite hard to get across to people who have understood and assimilated > >this sort of stuff, just how hard it feels to newcomers. We understand > >the explanations (we do! really! :-)) but even understanding them, we > >are still left with a lack of confidence. It's like being shown a full > >set of carpentry tools, having every one explained, but still reaching > >for the hammer every time and banging something no matter what we're > >trying to do :-) > > I had never heard of mapM, or other -M functions. I can't imagine why > those would be needed. It seems like pointless duplication.
The point of mapM is that you can use side-effects for each element processed. For example, with mapM in IO monad you can turn a list of filenames into a list of file contents. Actually, it is map that is redundant, because it's equivalent to mapM for the Identity monad. Best regards Tomasz -- I am searching for a programmer who is good at least in some of [Haskell, ML, C++, Linux, FreeBSD, math] for work in Warsaw, Poland _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe