Re: [Haskell-beginners] Does this function already exist in one of the standard modules?

Am Samstag 08 August 2009 22:01:34 schrieb I. J. Kennedy:

Does this function already exist in one of the standard modules? It computes f(f(f(...f(x))). I suspect it is a common function, but I can't find it, even using Hoogle.

applyMany :: Int -> (a -> a) -> a -> a applyMany 0 f x = x applyMany n f x = applyMany (n-1) f (f x)

Not directly, I think. But we have iterate :: (a -> a) -> a -> [a] iterate f x = x:iterate f (f x) so applyMany n f x = iterate f x !! n Most of the time you either need different numbers of iterations for the same starting value, then iterate is what you want, or the same number of iterations for different values, then you use something like let g = foldl (.) id (replicate n f) in ...