func exchange<T>(inout param1:T,inout param2:T){
  let tmp = param1
  param1 = param2
  param2 = tmp
}
var p1 = "15"
var p2 = "40"
exchange(&p1, param2: &p2)

struct Stack<ItemType> {
  var items:[ItemType] = []
  mutating func push(param:ItemType) {
    self.items.append(param)
  }
  mutating func pop()->ItemType{
    return self.items.removeLast()
  }
}
//整型栈
var obj1 = Stack<Int>()
obj1.push(1)
obj1.pop()
//字符串栈
var obj2 = Stack<String>()
obj2.push("HS")
obj2.pop()

extension Stack{
  func getArray() -> [ItemType] {
    return items
  }
}

class MyClass {
  
}
//只有MyClass的子类可以进行Stack栈的创建
struct Stack<ItemType:MyClass> {
  var items:[ItemType] = []
  mutating func push(param:ItemType) {
    self.items.append(param)
  }
  mutating func pop()->ItemType{
    return self.items.removeLast()
  }
}

protocol MyProtocol {
  //实现协议时才指定类型
  associatedtype ItemType
  var param:ItemType {get set}
}
class MyClass:MyProtocol {
  //由于Swift可以自动识别类型 这是MyProtocol中的ItemType为Int
  var param: Int = 0
}

//T和C都要遵守整型协议
class MyClassTwo<T,C where T:IntegerType,C:IntegerType> {
  var param1:T
  var param2:C
  init(param1:T,param2:C){
    self.param1=param1
    self.param2=param2
    
  }
}

var obj3 = MyClassTwo(param1: 1, param2: 1)