Distance between Int64 in Swift

Int64+Extensions.swift

extension Int64 {
    /*
     Returns the absolute distance between two Int64 values as a UInt64.
     A UInt64 is required to represent the range of possible distance values.
    */
    func distanceTo(_ other: Int64) -> UInt64 {
        if self == other {
            return 0
        }
        if self > other {
            return other.distanceTo(self)
        }
        
        let (distance, overflow) = other.subtractingReportingOverflow(self)
        if !overflow {
            return UInt64(distance)
        }
        
        // Int64.max minus any negative Int64 is too large to fit into an Int64. Convert it to a Uint64.
        // Take the difference between 0 and the negative number and add it to positive number, as UInt64
        let lowerDistance = self == Int64.min ? UInt64(Int64.max) + 1 : UInt64(-self)
        return lowerDistance + UInt64(other)
    }
}