This is actually half of the value of it. It allows you to easily change the implementation without breaking the public semantics. Generally speaking, the first-pass practice in Scala is to use public fields and to make them vals (final/C# readonly). Where you need to provide mutability, you use a var. But due to C#-esque properties, you can go from
var x = 1
to (not great code, but illustrative of the point)
private var _x: Int = 1
def x: Int = _x
def x_= (value: Int) = {
if (value > 1337)
throw new ArgumentOutOfRangeException()
_x = value
}
The convention is to use empty parents after zero-argument functions that have side effects, much like the ! in Scheme.
