swift3 Comparableプロトロル

Comparableプロトコルを作るには、
static func <(lhs: Even, rhs: Even) -> Bool
static func ==(lhs: Even, rhs: Even) -> Bool
の２つを実装すればよい。

struct M : Comparable 
{
    var val:Int
    
    static func <(lhs: M, rhs: M) -> Bool 
    {
        return lhs.val < rhs.val
    }
    
    static func ==(lhs: M, rhs: M) -> Bool
    {
        return lhs.val == rhs.val
    }
}

let r1 = M(val:1)
let p1 = M(val:2)
assert(r1 < p1)

let r2 = M(val:1)
assert(r1 == r2)