As an aside, in one of my libraries I have a combinator for folding a list in a binary-subdivision scheme.
> foldm :: (a -> a -> a) -> a -> [a] -> a > foldm (*) e x > | null x = e > | otherwise = fst (rec (length x) x) > where rec 1 (a : as) = (a, as) > rec n as = (a1 * a2, as2) > where m = n `div` 2 > (a1, as1) = rec (n - m) as > (a2, as2) = rec m as1 Then factorial can be defined more succinctly > factorial n = foldm (*) 1 [1 .. n] Cheers, Ralf _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
