Implementation of scala set.contains

Question

type Set = Int => Boolean
/**
* Indicates whether a set contains a given element.
*/
def contains(s: Set, elem: Int): Boolean = s(elem)

Why does

Answer 1

Set here is a function from Int to Boolean, so calling s(someInt) returns a boolean, you have of course to provide that function:

def contains(s: Set, elem: Int): Boolean = s(elem)

contains({ someInt => someInt == 1 }, 1) // returns true