Use functional combinators on Scala Tuples?

Question

\'map\' preserves the number of elements, so using it on a Tuple seems sensible.

My attempts so far:

scala> (3,4).map(_*2)    
error: value map is         


        

Answer 1

map function gets an A => B and returns F[B].

def map[A, B](f: A => B) : F[B]

As retronym wrote Tuple2[A, B] is a Bifunctor, so you can look for the bimap function in scalaz or cats.
bimap is a function that maps both sides of the tuple:

def bimap[A, B, C, D](fa: A => C, fb: B => D): Tuple2[C, D]

Because Tuple[A, B] holds 2 values and only one value can be mapped (by convention the right value), you can just return the same value for the left side and use the right function to map over the right value of the tuple.

(3, 4).bimap(identity, _ * 2)