enum AssertOp {
    case Equals
    case NotEquals
}

enum SimpleAssertOp {
    case NotNil
    case Nil
}

infix operator <=> { associativity left }
/**
 Asserts that the left hand side equals the right hand side and returns the left hand side.
 */
func <=><T : Equatable> (left : T?, right : (value :T?, op: AssertOp, file: StaticString, msg:  String, line : UInt)) -> T? {
    switch  right.op {
        case .Equals:
            XCTAssertEqual(left, right.value, right.msg, file: right.file, line: right.line)
        case .NotEquals:
            XCTAssertNotEqual(left, right.value, right.msg, file: right.file, line: right.line)
    }
    return left
}
func equals<T>(value : T?, message : String = "", file : StaticString = #file, line : UInt = #line) -> (T?, AssertOp, StaticString, String, UInt) {
    return (value, .Equals, file, message, line)
}

func notEquals<T>(value : T?, message : String = "", file : StaticString = #file, line : UInt = #line) -> (T?, AssertOp, StaticString, String, UInt) {
    return (value, .NotEquals, file, message, line)
}

func <=><T : Equatable> (left : T?, right : (op: SimpleAssertOp, file: StaticString, msg:  String, line : UInt)) -> T? {
    switch  right.op {
        case .Nil:
            XCTAssertNil(left, right.msg, file: right.file, line: right.line)
        case .NotNil:
            XCTAssertNotNil(left, right.msg, file: right.file, line: right.line)
    }
    return left
}

func notNil(message : String = "", file : StaticString = #file, line : UInt = #line) -> (SimpleAssertOp, StaticString, String, UInt){
    return (.NotNil, file, message, line)
}

func isNil(message : String = "", file : StaticString = #file, line : UInt = #line) -> (SimpleAssertOp, StaticString, String, UInt) {
    return (.Nil, file, message, line)
}