Hi. > while playing with folds and trying to implement `!!` by folding, I came to > the conclusion that: > > - `foldr` is unsuitable because it counts the elements from the end, while > `!!` needs counting from the start (and it's not tail recursive).
What is the problem with the following definition using foldr? > index :: Int -> [a] -> a > index n xs = > foldr > (\ x r n -> if n == 0 then x else r (n - 1)) > (const (error $ "No such index")) > xs > n Cheers, Andres _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
