Ryan Ingram wrote:
Just expand out the function composition:
Dual . Endo . flip f = (\x -> Dual (Endo (flip f x)))
which has the type d -> Dual (Endo c).
-- ryan
Aha.
I didn't get this straight away, but once I looked at the type signature for
function composition, it became clear.
Just expand out the function composition:
Dual . Endo . flip f = (\x -> Dual (Endo (flip f x)))
which has the type d -> Dual (Endo c).
-- ryan
On 8/26/07, Levi Stephen <[EMAIL PROTECTED]> wrote:
>
> Hi,
>
> I was browsing through the source code for Data.Foldable and having
> trouble
> com
Hi,
I was browsing through the source code for Data.Foldable and having trouble
comprehending it (which was kind of the point of browsing the code, so I could
learn something ;) )
I'm looking at foldl
foldl :: (c -> d -> c) -> c -> t d -> c
foldl f z t = appEndo (getDual (foldMap (Dual . End
