How to declare exponent/power operator with new precedencegroup in Swift 3?

Question

There\'s been a change in Swift 3 for Xcode 8 beta 6 and now I\'m not able to declare my operator for power as I did before:

infix operator ^^ { }
public fun         


        

Answer 1

Your code already compiles and runs – you don't need to define a precedence relationship or an associativity if you're simply using the operator in isolation, such as in the example you gave:

10 ^^ -12
10 ^^ -24

However, if you want to work with other operators, as well as chaining together multiple exponents, you'll want to define a precedence relationship that's higher than the MultiplicationPrecedence and a right associativity.

precedencegroup ExponentiativePrecedence {
    associativity: right
    higherThan: MultiplicationPrecedence
}

Therefore the following expression:

let x = 2 + 10 * 5 ^^ 2 ^^ 3

will be evaluated as:

let x = 2 + (10 * (5 ^^ (2 ^^ 3)))
//          ^^    ^^    ^^--- Right associativity
//          ||     \--------- ExponentiativePrecedence > MultiplicationPrecedence
//           \--------------- MultiplicationPrecedence > AdditionPrecedence,
//                            as defined by the standard library

The full list of standard library precedence groups is available on the evolution proposal.