Question

What is meant by below scala declaration :

type MyType = Int => Boolean

Here is my understanding :

I’m declaring a new type ‘MyType’ but what is meant by the higher order function ‘Int => Boolean’

Answer 1

It’s not so much declaring a new type as declaring a new type alias. They’re still the same type: but the alias lets your write it a little more succinctly.

Int => Boolean is the type of a function that takes one argument, an Int, and returns a Boolean.

For example, a function like “greater than 5” could have type Int => Boolean:

type MyType = Int => Boolean
val greaterThan5: MyType = (x: Int) => x > 5
greaterThan5(7)  // true