C++找对象的季节（补）——方程类

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#include <iostream>using namespace std;class CEquation{private:    double a;     // 未知数系数    double b;     // 常数项    char unknown; // 代表未知数的符号public:    CEquation(double aa=0,double bb=0);    friend istream &operator >> (istream &in,CEquation &e);    friend ostream &operator << (ostream &out,CEquation &e);    double Solve();    char getUnknown();};CEquation::CEquation(double aa,double bb){    a=aa;    b=bb;}istream &operator >> (istream &in,CEquation &e){    char x,y;    double c;    in>>e.a>>x>>e.b>>y>>c;    while (1)    {        if (x>='a'&&x<='z'&&y=='='&&c==0) break;        else            cout<<"格式不对，重新输入。"<<endl;        in>>e.a>>x>>e.b>>y>>c;    }    e.unknown=x;    return in;}ostream &operator << (ostream &out,CEquation &e){    cout<<e.a<<e.unknown;    if (e.b>0)        cout<<'+';    cout<<e.b<<"=0"<<endl;    return out;}double CEquation::Solve(){    double x;    x=-b/a;    return x;}char CEquation::getUnknown(){    return unknown;}int main(){    CEquation e;    cout<<"请输入方程(格式：ax-b=0，a、b为常数，x处是代表未知数的字母)：";    cin>>e;   //在两次测试中，分别输入3x-8=0和50s+180=0    cout<<"方程为："<<e;    cout<<"方程的解为："<<e.getUnknown()<<"="<<e.Solve()<<endl; //对两次测试，分别输出x=...和s=...    e.Solve();}

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