Prefix Operator Example...

Following are the only allowed Prefix Operators #123

1. +
2. -
3. !
4. ~

scala> val no = -5
no: Int = -5

scala> val no = 5.unary_-
no: Int = -5

scala> val no = 5.unary_-()
<console>:23: error: Int does not take parameters
       val no = 5.unary_-()
                         ^