pub fn combine(&self, x: i64, y: i64) -> i64 {
        match self {
            Operation::Sum => x + y,
            Operation::Product => x * y,
        }
    }
/// Apply the operation to operands, yielding a new tally.
Apply the operation to operands, yielding a new tally.
Apply the operation to operands yielding a new tally .
pub fn combine(&self, x: i64, y: i64) -> i64 {
        match self {
            Operation::Sum => x + y,
            Operation::Product => x * y,
        }
    }
pub fn combine ( & self , x : i64 , y : i64 ) -> i64 { match self { Operation :: Sum => x + y , Operation :: Product => x * y , } }
Apply the operation to operands, yielding a new tally.
Apply the operation to operands yielding a new tally .
&self
x
i64
y
i64