Question

In Haskell, I can easily map a list:

map (\x -> 2*x) [1,2]

gives me [2,4]. Is there any “mapTuple” function which would work like that?

mapTuple (\x -> 2*x) (1,2)

with the result being (2,4).

Answer 1

Searching at Hoogle gives no exact matches for (a -> b) -> (a, a) -> (b, b), which is the type you require, but it is pretty easy to do yourself:

mapTuple :: (a -> b) -> (a, a) -> (b, b)
mapTuple f (a1, a2) = (f a1, f a2)

Note, you will have to define a new function for 3-tuples, 4-tuples etc – although such a need might be a sign, that you are not using tuples like they were intended: In general, tuples hold values of different types, so wanting to apply a single function to all values is not very common.