Null-coalescing operator for Swift

nullcoalescing.swift

// "A !|| B" returns unwrapped value of A if it is not nil, or B if it is
operator infix !|| { associativity left }
func !|| <T>(lhs: T?, rhs: T) -> T {
    if let unwrappedValue = lhs {
        return unwrappedValue;
    } else {
        return rhs;
    }
}

let dic = [1:"One", 2:"Two", 3:"Three"]

dic[1] !|| "missing"                      // "One"
dic[4] !|| "missing"                      // "missing"
dic[4] !|| dic[5] !|| "missing"           // "missing"
dic[4] !|| dic[2] !|| "missing"           // "Two"

var x: Int?
x !|| 99                                  // 99
x = 1
x !|| 99                                  // 1
x = nil
x !|| 99                                  // 99