项目4

#include<iostream>
using namespace std;
class CEquation
{private:
	double a;     // 未知数系数
	double b;     // 常数项
	char unknown; // 未知数的符号
public:
	CEquation(double aa=0,double bb=0){ a=aa;b=bb;}
	friend istream &operator >> (istream &in,CEquation &e);
	friend ostream &operator << (ostream &out,CEquation &e);
	double Solve();   //返回解方程的结果
	char getUnknown();   //返回未知数用什么符号
};
double CEquation::Solve(){

 return  -b/a;
}
char CEquation::getUnknown(){
  return unknown;
}
istream &operator >> (istream &in,CEquation &e){
     char x,y;
 in>>e.a>>e.unknown>>e.b>>x>>y;
  while(x!='=' || y!='0')
  in>>e.a>>e.unknown>>e.b>>x>>y;
  return in;
}
ostream &operator << (ostream &out,CEquation &e){
   out<<e.a<<e.getUnknown();
   if(e.b>0)
   out<<"+"<<e.b;
   else
   out<<e.b;
   out<<"="<<"0";
   return out;
}
int main()
{
	CEquation e;
	cout<<"请输入一元一次方程(输入格式：3x-8=0)：";
	cin>>e;   //在两次测试中，分别输入3x-8=0和5s+18=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();
	return 0;
}

运行结果：