Comparable+Additions.swift

import Foundation


enum Position {
    case Over
    case Under
}

extension Comparable {
    func isBetween<T where T: Comparable>(lhs: T, _ rhs: T) -> (Bool, Position?) {
        assert(self is T, "\(self) of type \(self.dynamicType), is not comparable to the provided parameters of type \(T.self).")
        if let someSelf = self as? T {
            if someSelf >= lhs && someSelf <= rhs {
                return (true, nil)
            } else if someSelf < lhs {
                return (false, Position.Under)
            } else if someSelf > rhs {
                return (false, Position.Over)
            }
        }
        return (false, nil)
    }
}

//MARK: Example
//
//
//let number = 7
//
//switch number.isBetween(1, 10) {
//case (true, nil):
//    print("between")
//case (false, .Some(.Over)):
//    print("over")
//case (false, .Some(.Under)):
//    print("under")
//default:
//    print("other")
//}