Symmetrical operators


Not symmetrical by default, but able to add an attribute/keyword to auto-generate a default implementation which swaps the lhs & rhs.


Hi, list!

I’m thinking about proposal that would add a possibility to save some time on creating symmetrical binary operators.

The latest code example from my math lib:

    public static func *(lhs: Angle, rhs: Float) -> Angle {
        return Angle(lhs.degrees * rhs)
    public static func *(lhs: Float, rhs: Angle) -> Angle {
        return Angle(rhs.degrees * lhs)

The API of Angle doesn’t really matter here, what’s important is that I have to write another operator to make it symmetrical. Not so hard: 3 lines of code. It can even refer to original implementation, instead of duplicating the logic. But I think it would be nice to have something like symmetrical keyword, just like we have associativity and precedence.

I also bet that all operators should be asymmetrical by default.

Any thoughts?