Hi,
If we omit an argument in a function call, Scala will take the default value we provided for it.
scala> def func(a:Int,b:Int=7){
| println(a*b)
| }
func: (a: Int, b: Int)Unit
scala> func(2,5)
10
scala> func(2)
But make sure that any default arguments must be after all non-default arguments.