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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.

Jonathan Fischoff
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3 Answers3

3

Here is an example to achieve this using Template Haskell.

ChrisJ
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3

The tuple library provides lots of these sorts of functions.

John L
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1

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)

barsoap
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