数据结构、算法与应用 （C++描述） 第二版 1.18

    关于练习1.17，直接用这个就可以了。[数据结构、算法与应用 （C++描述） 第二版 1.16](http://blog.csdn.net/tianluoyuge/article/details/49863769)    关于1.18，重载了**+、-、*、/**和**>>**运算符，对于>>他要求不能写在**公有成员函数**里，所以用**友元**写，**关于+、-运算我写的比较啰嗦，是为了检测正负符号**，因为存储和输出的时候都是按照sign的值来显示符号，而amount里面是正值            **仅供有需要的人以参考，如有错误请纠正我**

头文件：currency.h

#ifndef CURRENCY_H_#define CURRENCY_H_#include<iostream>#include<exception>enum signType { plu, minu };class currency{private:    signType sign;    long amount;public:    currency(signType theSign = plu, unsigned long theDollars = 0, unsigned int theCents = 0);    ~currency() { }    void operator=(int x);    void operator=(double theAmount);    signType getSign() const;    unsigned long getDollars() const;    unsigned int getCents() const;    currency operator+(const currency & x) const;    currency operator-(const currency & x) const;    currency operator*(const currency & x) const;    currency operator/(const currency & x) const;    friend std::ostream & operator<<(std::ostream & out, const currency &x);    friend std::istream & operator>>(std::istream & in, currency & x);};#endif

头文件实现：currency.cpp

#include"currency.h"currency::currency(signType theSign, unsigned long theDollars, unsigned int theCents)    : sign(theSign){    using namespace std;    if (theCents > 99)    {        cerr << "Cents should be < 100";        exit(EXIT_FAILURE);    }        amount = theDollars * 100 + theCents;    if (theSign == minu)        amount = -amount;}void currency::operator=(int x){    if (x < 0)    {        sign = minu;        amount = -x;    }    else    {        sign = plu;        amount = x;    }}void currency::operator=(double theAmount){    if (theAmount < 0)    {        amount = (long)((theAmount - 0.001) * 100);        sign = minu;        amount = -amount;    }    else        amount = (long)((theAmount + 0.001) * 100);}signType currency::getSign() const{    if (amount < 0)        return minu;    else        return plu;}unsigned long currency::getDollars() const{    if (amount < 0)        return (-amount) / 100;    else        return amount / 100;}unsigned int currency::getCents() const{    if (amount < 0)        return -amount - getDollars() * 100;    else        return amount - getDollars() * 100;}currency currency::operator+(const currency & x) const{    currency result;    if (sign == plu && x.sign == plu)        result.amount = amount + x.amount;    else if (sign == plu && x.sign == minu)    {        if (amount > x.amount)        {            result.amount = amount - x.amount;            result.sign = plu;        }        else        {            result.amount = x.amount - amount;            result.sign = minu;        }    }    else if (sign == minu && x.sign == plu)    {        if (amount > x.amount)        {            result.amount = amount - x.amount;            result.sign = minu;        }        else        {            result.amount = x.amount - amount;            result.sign = plu;        }    }    else if (sign == minu && x.sign == minu)    {        result.amount = amount + x.amount;        result.sign = minu;    }    return result;}currency currency::operator-(const currency & x) const{    currency temp;    if (sign == plu && x.sign == plu)    {        if (amount > x.amount)            temp.amount = amount - x.amount;        else        {            temp.amount = x.amount - amount;            temp.sign = minu;        }    }    else if (sign == plu && x.sign == minu)    {        temp.amount = amount + x.amount;        temp.sign = plu;    }    else if (sign == minu && x.sign == plu)    {        if (amount > x.amount)        {            temp.amount = amount - x.amount;            temp.sign = minu;        }        else            temp.amount = x.amount - amount;    }    else if (sign == minu && x.sign == minu)    {        temp.amount = amount + x.amount;        temp.sign = minu;    }    return temp;}currency currency::operator*(const currency & x) const{    currency temp;    temp.amount = amount * x.amount;    if (sign == minu || x.sign == minu)        temp.sign = minu;    return temp;}currency currency::operator/(const currency & x) const{    currency temp;    double t1 = amount;    double t2 = x.amount;    double tt = t1 / t2;    temp.amount = tt * 100;    if (sign == minu || x.sign == minu)        temp.sign = minu;    return temp;}std::ostream & operator<<(std::ostream & out, const currency & x){    if (x.sign == minu)        out << '-';    long dollars = x.amount / 100;    out << '$' << dollars << '.';    int cents = x.amount - dollars * 100;    if (cents < 10)        out << '0';    out << cents;    return out;}std::istream & operator>>(std::istream & is, currency & x){    long temp;    is >> temp;    if (temp > 0)    {        x.amount = temp;        x.sign = plu;    }    else    {        x.amount = -temp;        x.sign = minu;    }    return is;}

测试文件：main.cpp

#include"currency.h"#include<iostream>#include<cstdlib>int main(){    using namespace std;    currency g, i, j;    currency h(plu, 3, 50);    g = 25;    i = -6.45;    cout << "g: " << g << endl;    cout << "i: " << i << endl;    j = h + g;    cout << h << " + " << g << " = " << j << endl;    j = i + g + h;    cout << i << " + " << g << " + " << h << " = " << j << endl;    currency t1;    t1 = 100;    currency t2;    t2 = -50;    currency t3;    t3 = t1 * t2;    cout << "t3: " << t3 << endl;    cout << "Enter a number: ";    cin >> t3;    cout << "t3: " << t3 << endl;    t3 = t1 / t2;    cout << t1 << " / " << t2 << " = " << t3 << endl;    t3 = t1 - t2;    cout << t1 << " - " << t2 << " = " << t3 << endl;    return 0;}