Kleisli[Future, Context, \/] 到 Kleisli[EitherT, Context, ...] [英] Kleisli[Future, Context, \/] to Kleisli[EitherT, Context, …]

问题描述

因为我想结合适用于长方法 Future 的 Kleisli 可能会失败 Either，所以我需要叠加效果.这是在 Kleisli 中堆叠效果的结果代码.scalaz 中是否有现有的组合器?

As I want to combine Kleisli that works on long methods Future that can fail Either, I need to stack the effect. Here is the resulting code to stack the effect in the Kleisli. Is there an existing combinator in scalaz ?

type FutureEitherT[A] = EitherT[Future, String, A]

def toKleisliEitherTFromDisjunction[A](f: Kleisli[Future, Context,String \/ A]) = 
  Kleisli[FutureEitherT, Context, A] { ctx => EitherT(f(ctx)) }

我试过没有成功 f.liftMK[FutureEitherT]，但不幸的是，Kleisli 类型构造函数中的第三个类型仍然是一个 Either.

I've tried without success f.liftMK[FutureEitherT], but unfortunately, the third types in the Kleisli type constructor is still an Either.

推荐答案

你可以使用 mapK:

import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global
import scalaz.{\/, EitherT, Kleisli}
import scalaz.std.scalaFuture

type FutureEitherT[A] = EitherT[Future, String, A]

val futureK: Kleisli[Future, Int, String \/ Int] = 
  Kleisli.ask[Future, Int] map (i => \/.right[String, Int](i)))

futureK mapK[FutureEitherT, Int]( EitherT.eitherT )
// scalaz.Kleisli[FutureEitherT,Int,Int] = Kleisli(<function1>)

这篇关于Kleisli[Future, Context, \/] 到 Kleisli[EitherT, Context, ...]的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！