The Neg trait enables a data type to be used with the unary negation operator, also known as the negative sign. When we write -5, we're applying the unary negation operator to the value 5, producing a negative 5 as the result.

Implementing Neg looks like this:

pub enum NegExample {
 Yes,
 No,
}

impl Neg for NegExample {
 type Output = NegExample;

 fn neg(self) -> NegExample {
 match self {
 NegExample::Yes => NegExample::No,
 NegExample::No => NegExample::Yes,
 }
 }
}