scala - When should one use a Kleisli? - Stack Overflow
2020年5月20日 · "Kleisli" by itself isn't a thing. The concept of a Kleisli arrow comes from category theory, but in Haskell you can think of it as a generalization of a function. Given a function f :: a …
How to use Kleisli arrows with monads? - Stack Overflow
2017年1月2日 · Using the arrow notation we can rewrite computing one file name as a Kleisli arrow: {-# LANGUAGE Arrows #-} import Control.Arrow import System.Directory import …
What problem does the Kleisli arrows solve in fp-ts?
2022年5月23日 · These helpers you've listed are there for when you already have a Kleisli arrow and you want to use it with some other Functor values. In the example they have. declare …
Function composition, Kleisli arrow, and Monadic laws
2014年2月1日 · Yes, they do conform. And that they conform is indeed the reason they are called Kleisli, because the Kleisli arrows plus types form the Kleisli category of the monad (to which …
What are arrows, and how can I use them? - Stack Overflow
2010年11月16日 · The arrow typeclass takes three type arguments: the arrow type, the input type, and the output type. Looking at the instance head for arrow instances we find: instance …
haskell - Lift Kleisli arrow into IO? - Stack Overflow
2012年11月22日 · stdoutProcessA :: Kleisli (MaybeT IO) String String writeToFileA :: Kleisli (MaybeT IO) (FilePath, String) () If you write your other arrows as Monad m => Kleisli (MaybeT …
Why there isn't a Functor instance for Kleisli in Control.Arrow?
2013年9月21日 · While trying to familiarize myself with Control.Arrow, I have noticed that the Kleisli newtype would seem to admit a Functor instance, something like: instance Monad m => …
Why does kleisli composition expect a pure value?
A Kleisli arrow from a to b is defined as a function a -> m b. Let's notate it a ~> b (leaving the m assumed). What does it mean to compose two of these arrows?
Application of functions and Kleisli arrows - Stack Overflow
2016年10月16日 · Both your examples are arrow mappings of functors (not Functors, but functors in the broader categorical sense), just like fmap is the arrow mapping of a Functor. (=<<), for …
Kleisli Arrow with Writer in Scala. Why doesn't it compile?
2014年2月10日 · val ff = Kleisli.kleisliU(f) >=> Kleisli.kleisliU(f) kleisliU is essentially just a nice version of Kleisli.apply that uses a new type class (named Unapply) behind the scenes to …