[Haskell-cafe] Seeking help to generalize this ..

[Debasish Ghosh]

I finally ended up defining a combinator

flattenAndCompose :: (Category cat) => [cat a a] -> cat a a
flattenAndCompose = foldr (>>>) id

that can be used both for function composition and Kleislis since both (->)
and Kleisli are instances of Category. I will take a look at Endo - thanks
for the pointer ..

regards.



On Fri, Feb 7, 2020 at 11:26 PM Matthew Farkas-Dyck <strake888 at gmail.com>
wrote:

> On 2/1/20, Jack Kelly <jack at jackkelly.name> wrote:
> > In Data.Monoid there is the 'Endo' newtype, which wraps functions of
> > type 'a -> a'. Is there an 'EndoM' variant, or is that something that's
> > usually created by putting other pieces together? Below is a sketch of
> > what I mean:
> >
> > -- Maybe this is known by another name?
> > newtype EndoM f a = EndoM { appEndoM :: a -> f a }
>
> I define a general `Endo` type in the category package, here:
>
> http://hackage.haskell.org/package/category-0.2.5.0/docs/Data-Morphism-Endo.html
>
> Thus one can use `Endo (Kleisli m)`.
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-- 
Debasish Ghosh
http://manning.com/ghosh2
http://manning.com/ghosh

Twttr: @debasishg
Blog: http://debasishg.blogspot.com
Code: http://github.com/debasishg
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