TIL how to extend all floating point types at ones in Swift

About a month ago, on 13 of January, I have written about exnending all float types (Float, CGFloat, Double and Float80) at once by extending FloatingPoint. This day come. After writing 100 times function for conversion from degrees to radians and vise versa I decided it’s time to write something generic. It turns out not to be that easy.

Intension is to write following, but generic:

extension Double {
    var inRadians: Double {
        return self / (180.0 * Double.pi)
    }
}

This is working:

extension BinaryFloatingPoint {
    func inRadians<T>() -> T where T: BinaryFloatingPoint {
        return T(self) / (T(180.0) * T.pi)
    }
}

First, failed to make it for FloatingPoint just because haven’t found way to cast literal 180.0 (which is Double) to FloatingPoint. Strange. Second, appearance of T here is artificial. There’s no way to get rid of T and use just BinaryFloatingPoint. Third, I haven’t found a syntax to make it work for property, not for a function. Should be possible something like this, but it isn’t working:

extension BinaryFloatingPoint {
    var inRadians: <T> where T: BinaryFloatingPoint { // compiler gets mad here
        return T(self) / (T(180.0) * T.pi)
    }
}