Or using the lens package:
:m Data.Foldable Control.Lens Data.Monoid.Lens ala _endo foldMap [(+1), (*2)] 8 17
On Sat, Oct 27, 2012 at 1:01 AM, Tony Morris
** It's the Endo monoid.
λ> :t ala Endo foldMap -- see newtype package ala Endo foldMap :: Foldable t => t (a -> a) -> a -> a λ> ala Endo foldMap [(+1), (*2)] 8 17 λ> :i ala ala :: (Newtype n o, Newtype n' o') => (o -> n) -> ((o -> n) -> b -> n') -> b -> o' -- Defined in Control.Newtype
On 27/10/12 04:41, Greg Fitzgerald wrote:
Hi Haskellers,
I've recently found myself using the expression: "foldr (.) id" to compose a list (or Foldable) of functions. It's especially useful when I need to map a function over the list before composing. Does this function, or the more general "foldr fmap id", defined in a library anywhere? I googled and hoogled, but no luck so far.
Thanks, Greg
_______________________________________________ Haskell-Cafe mailing listHaskell-Cafe@haskell.orghttp://www.haskell.org/mailman/listinfo/haskell-cafe
-- Tony Morrishttp://tmorris.net/
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe