On Fri, May 04, 2007 at 19:23:16 +0200, Phlex wrote:
Hello all,
I'm trying to learn haskell, so here's is my first newbie question. I hope this list is appropriate for such help requests.
I'm trying to write a function with the signature [IO Int] -> IO [Int]
Here is my first attempt :
conv :: [IO Int] -> IO [Int] conv l = do val <- (head l) return (val : (conv (tail l)))
This does not work as I'm consing an Int to an (IO [Int]). So I tried this :
conv2 :: [IO Int] -> IO [Int] conv2 l = do val <- (head l) rest <- (conv2 (tail l)) return (val : rest)
That works, but it won't work for infinite lists. How could I achieve the desired result ?
I had a similar problem a little while back. I also asked on this list and maybe that discussion[1] can illuminate the issue. I also put an entry on my blog afterwards in an attempt to capture my understanding of it all[2]. /M [1]: http://www.haskell.org/pipermail/haskell-cafe/2007-January/021367.html [2]: http://therning.org/magnus/archives/249 -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus@therning.org Jabber: magnus.therning@gmail.com http://therning.org/magnus