任何遵循Equatable的类型，都需要实现方法static func ==(lhs: Self, rhs: Self) -> Bool在这个方法内按照指定的值和值间对比关系返回true或是false，外部表现为==或是!=的结果
struct Human: Equatable {
var name: String
var age = 5
static func == (lhs: Self, rhs: Self) -> Bool {
return lhs.name == rhs.name
}
}
let tom = Human(name: "tom", age: 5)
let tim = Human(name: "tim", age: 6)
tom == tim // false
let man1 = Human(name: "tom", age: 5)
let man2 = Human(name: "tom", age: 6)
man1 == man2 // true
