Question

What is the following methods’ difference?

def sum1() = 1+2

def sum2(a:Unit) = 1+2

I think they are semantically identical, is it right?

Answer 1

With sum1, you can call it with or without parentheses:

val x = sum1    // x: Int = 3
val y = sum1()  // y: Int = 3

But with sum2 you are forced to provide parentheses.. I think that if you call sum2(), you are actually calling sum2 with () as the argument a.

val x2 = sum2   // error
val y2 = sum2() // y2: Int = 3