c++ prime plus 第十一章 第6题

前几天开始上课，偶尔翻了一下c++第十一章。主要讲了重载，友元，类型转换。。。

跳过了随机函数的那一小块。现在，基本上结合书可以写出这一章的内容，实现重载，友元，类型转换等。还不是很熟练，可以以后多练练书后面的习题。

//stonewt.h

#ifndef STONEWT_H_INCLUDED#define STONEWT_H_INCLUDED#include <iostream>//没有用状态成员mode//没有过多的使用转换函数using namespace std;class Stonewt{private:    enum {Lbs_per_stn = 14};    int stone;    double pds_left;    //几英石几英磅    double pounds;      //英磅public:    Stonewt(double pou);    Stonewt(int sto,double pds);    Stonewt();    ~Stonewt();//operater overloading    Stonewt operator+(const Stonewt & b) const;    Stonewt operator-(const Stonewt & b) const;    Stonewt operator*(double n) const;    bool operator<(const Stonewt& b) const;    bool operator<=(const Stonewt& b) const;    bool operator==(const Stonewt& b) const;//返回类型//friends    friend Stonewt operator*(double n,const Stonewt & b);    friend ostream & operator<<(ostream & os, Stonewt & st);    friend bool operator>(Stonewt& a, Stonewt& b);    friend bool operator>=(Stonewt& a, Stonewt& b);    friend bool operator!=(Stonewt& a, Stonewt& b);};#endif // STONEWT_H_INCLUDED

//stonewt

#include "stonewt.h"Stonewt::Stonewt(double pou){    stone = int(pou) / Lbs_per_stn;    pds_left = int(pou) % Lbs_per_stn + pou - int(pou);    pounds = pou;}Stonewt::Stonewt(int sto,double pds){    stone = sto;    pds_left = pds;    pounds = sto * Lbs_per_stn + pds;}Stonewt::Stonewt(){    stone = pounds = pds_left = 0;}Stonewt::~Stonewt(){}//operater overloadingStonewt Stonewt::operator+(const Stonewt & b) const{    return Stonewt(pounds+b.pounds);}Stonewt Stonewt::operator-(const Stonewt & b) const{    return Stonewt(pounds-b.pounds);}Stonewt Stonewt::operator*(double n) const{    return Stonewt(pounds*n);}//第一次尝试重载<,==等关系运算符bool Stonewt::operator<(const Stonewt& b) const{    if(pounds<b.pounds)        return 1;    else        return 0;}bool Stonewt::operator<=(const Stonewt& b) const{    return pounds <= b.pounds;}bool Stonewt::operator==(const Stonewt& b) const{    return pounds == b.pounds;}//friendsbool operator>(Stonewt& a, Stonewt& b){    return a.pounds > b.pounds;}bool operator>=(Stonewt& a, Stonewt& b){    return a.pounds >= b.pounds;}bool operator!=(Stonewt& a, Stonewt& b){    return a.pounds != b.pounds;}Stonewt operator*(double n,const Stonewt & b){    return b*n;}ostream& operator<<(ostream& os, Stonewt & st){    os << st.pounds << " pounds,or " << st.stone << " stone and " << st.pds_left << " pounds." << std::endl;    return os;}

//c++pp11.9.6.cpp

#include <iostream>#include "stonewt.h"#include <cstdlib>using namespace std;int main(int argc, const char * argv[])  //?{    Stonewt a(12);    a = 154;//转换函数    cout << a;    int num=1;    Stonewt b[7] = { 123, 23.32, 3.3 };    b[3]= b[1] + b[2];    b[4]= 10 * b[3];    for (int i = 5; i < 7; i++)    {        b[i] = rand();//随机数我还不是很明白    }    cout << endl;    cout << "7个Stonewt的输出：" << endl;    for (int i = 0; i < 7; i++)    {        cout << b[i];    }    cout << endl;    Stonewt min = b[0];    Stonewt max = b[0];    for (int i = 0; i < 7; i ++)    {        if (min > b[i])        {            min = b[i];        }        if (max < b[i])        {            max = b[i];        }        if (b[i] >= a)        {            num++ ;        }    }    cout << "Min: " << min ;    cout << "Max: " << max ;    cout << "bigger than 11: " << num << "个。" << endl;    return 0;}