元组函数的N-Ary版本

Question

Is there a library that has n-ary versions of tuple functions like first , *** , etc, through Template Haskell (or using some other method).

Ideally I would like to able to say

$(select 3 [0, 1])

which we make the lambda

\(x, y, z) -> (x, y)

and for a generic *** for functions

$(tapply 3 [(0, "f"), (1, "g"), (2, "h")])

which would make the lambda

\f g h (x, y, z) -> (f x, g y, h z)

Other n-ary functions would also be nice, but those are the two I need currently.

Answer 1

这是使用Template Haskell实现此目的的示例 。

Answer 2

元组库提供了许多这类功能。

Answer 3

Generally, I'd say you want to use a proper ADT instead, and libraries like bifunctor , or, if it gets more complex than that, a proper generics library. (That link could be more up to date... if in doubt, and you don't have especially high performance requirements, just use SYB )