为什么这样写就是对的，也就是说允许有私有变量，但不许有私有方法么？？

Question

#include <iostream>using namespace std;enum BREED (Golden,Cairn, Lab, Schnauzer); struct Mammal{Mammal(): Age(0),Weight(0){};~Mammal(){};virtual void setAge(int age){this->Age=age;}virtual int getAge(){return Age;}virtual void setWeight(int weight){this->Weight=weight;}virtual int getWeight(){return Weight;}protected: int Age,Weight;};struct Dog:public Mammal{Dog(): Mammal(){};~Dog();BREED getBreed(){return breed;}void setBreed(BREED b){this->breed=b;}private BREED breed;void Bark(){cout<<"Bark!!"<<endl;}  };int main(){Dog Argo;Argo.Bark();cout<<Argo.getAge()<<endl;;system("pause");return 0;}这段代码哪里错了，怎么改正？另附：枚举的用法是怎样，枚举列的名字是否可以当成一个类来使用？？void Bark(){cout<<"Bark!!"<<endl;}  private :BREED breed;

Answer 1

#include <iostream>
#include <stdlib.h>

using namespace std;

enum BREED {Golden,Cairn, Lab, Schnauzer}; //不是 （）而是{ } 

struct Mammal{

Mammal(): Age(0),Weight(0){};
~Mammal(){};

virtual void setAge(int age){this->Age=age;}
virtual int getAge(){return Age;}
virtual void setWeight(int weight){this->Weight=weight;}
virtual int getWeight(){return Weight;}
protected: int Age,Weight;

};

struct Dog:public Mammal{

Dog(){breed=Lab;};//这里有错 

~Dog(){};
BREED getBreed(){
return breed;
}
void setBreed(BREED b){
this->breed=b;
}

BREED breed;//把private去掉就行了  

void Bark(){
cout<<"Bark!!"<<endl;
}  

};

int main(){

Dog Argo;  
Argo.Bark();
cout<<Argo.getAge()<<endl;;

system("pause");
return 0;
}

如果一个变量只有几种可能的值，可以定义为枚举类型。
枚举类型就是将变量的值一一列举出来，变量的值仅限于列举出来的值的范围内。
enum {sun, mon, tue, wed, thu, fri, sat} workday, weekend ;
其中sun, mon,....,sat称为枚举元素或枚举常量，为用户定义的标识符，所代表的意义由用户决定，在程序中体现出来。
1、枚举元素为常量，不可赋值运算。 sun=0; mon=1;
2、在定义枚举类型的同时，编译程序按顺序给每个枚举元素一个对应的序号，序号从0开始，后续元素依次加1。
3、可以在定义时人为指定枚举元素的序号值。
enum weekday {sun=9, mon=2, tue, wed, thu, fri, sat};
4、只能给枚举变量赋枚举值，若赋序号值必须进行强制类型转换。

 

Answer 2

#include "iostream"
using namespace std;

class CPU
{
public:
CPU(int a,int b,double c);
CPU(CPU &);
int getfr(){ return frequency; }
int getwo(){ return wordlength; }
double getco(){ return coefficient; }
void run(){ cout<<"run"<<endl; }
void stop(){ cout<<"stop"<<endl; }

private:
int frequency;
// 枚举体中的类型别名表中使用的是标识符，不能使用数字
// 倘若W8、W16等都没有赋值的则W8、W16等值分别为0,1,2,3,4,5,6
// 倘若{W8,W16=16,W16,W32,W64,W128,W256}则值分别为0,16,17,18,19,20
enum cpu_len {W8=8,W16=16,W32=32,W64=64,W128=128,W256=126}wordlength;
double coefficient;
};

CPU::CPU(int a,int b,double c)
{
frequency=a;
// 在不改变你原有枚举体隐藏属性的前提下修改如下
switch(b)
{
case 1 : wordlength = W8; break;
case 2 : wordlength = W16; break;
case 3 : wordlength = W32; break;
case 4 : wordlength = W64; break;
case 5 : wordlength = W128; break;
case 6 : wordlength = W256; break;
default : break;
}
coefficient=c;
cout<<"构造函数被调用"<<endl;
}

CPU::CPU(CPU &L):frequency(L.frequency),wordlength(L.wordlength),coefficient(L.coefficient)
{
cout<<"拷贝构造函数被调用"<<endl;
}

int main()
{
CPU cpu1(4,1,4.0);
CPU cpu2(cpu1);
cout<<"cpu1"<<endl;
cout<<"主频："<<cpu1.getfr()<<"MHz"<<"字长："<<cpu1.getwo()<<"倍频："<<cpu1.getco()<<endl;
cout<<"cpu2"<<endl;
cout<<"主频："<<cpu2.getfr()<<"MHz"<<"字长："<<cpu2.getwo()<<"倍频："<<cpu2.getco()<<endl;
}