元组有类似的 zipWith 吗? [英] Is there a zipWith analogue for tuples?

问题描述

初步说明:这是对 SeanD 删除的问题 的重制.>

就像列表有 zipWith 一样...

GHCi>zipWith (+) [1,2] [3,4][4,6]

...感觉应该有类似元组的东西，本着...的精神.

tupleZipWith (+) (1,2) (3,4)

...但在base中似乎没有明显类似的东西.我有哪些选择?

解决方案

一种选择是使用 tuples-homogenous-h98 包，它为具有适当 Applicative 实例的同构元组提供新型包装器:

GHCi>导入 Data.Tuple.HomogenousGHCi>进口控制.ApplicativeGHCi>LiftA2 (+) (Tuple2 (1,2)) (Tuple2 (3,4))元组 2 {untuple2 = (4,6)}GHCi>(>) <$>元组 3 (7,4,7) <*>元组 3 (6,6,6)Tuple3 {untuple3 = (True,False,True)}

如果你有一个除了 tuples-homogenous-h98 之外最喜欢的同构元组/固定大小向量/固定大小列表库，那么它很可能也有合适的 ZipListcode>-like Applicative 实例.

<小时>

对于对的问题略有不同的看法，您可能需要考虑 Data.Biapplicative 来自 bifunctors:

GHCi>导入 Data.BiapplicativeGHCi>bimap (+) (+) (1,2) <<*>(3,4)(4,6)

这种方法的一个好处是它可以处理异构对:

GHCi>bimap (+) (+) (1,2.5) <<*>(3,4)(4,6.5)GHCi>bimap (+) (++) (1,"foo") <<*>>(3,酒吧")(4,"foobar")

Preliminary note: this is a respin of a deleted question by SeanD.

Just like there is zipWith for lists...

GHCi> zipWith (+) [1,2] [3,4]
[4,6]

... it feels like there should be something analogous for tuples, in the spirit of...

tupleZipWith (+) (1,2) (3,4)

... but there doesn't seem to be anything obviously like that in base. Which options do I have?

解决方案

One option is using the tuples-homogenous-h98 package, which provides newtype wrappers for homogeneous tuples that have appropriate Applicative instances:

GHCi> import Data.Tuple.Homogenous
GHCi> import Control.Applicative
GHCi> liftA2 (+) (Tuple2 (1,2)) (Tuple2 (3,4))
Tuple2 {untuple2 = (4,6)}
GHCi> (>) <$> Tuple3 (7,4,7) <*> Tuple3 (6,6,6)
Tuple3 {untuple3 = (True,False,True)}

If you have a favourite homogenous tuple/fixed-size vector/fixed-size list library other than tuples-homogenous-h98, odds are that it will also have suitable ZipList-like Applicative instances.

---

For a slightly different take on the matter when it comes to pairs, you might want to consider Data.Biapplicative from bifunctors:

GHCi> import Data.Biapplicative
GHCi> bimap (+) (+) (1,2) <<*>> (3,4)
(4,6)

One nice thing about this approach is that it can handle heterogeneous pairs:

GHCi> bimap (+) (+) (1,2.5) <<*>> (3,4)
(4,6.5)
GHCi> bimap (+) (++) (1,"foo") <<*>> (3,"bar")
(4,"foobar")

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