C++ 错误：“ostream”未命名类型
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error: ‘ostream’ does not name a type
提问by user2741941
I am overloading the << and >> operator in C++, but it cannot compile.
我在 C++ 中重载了 << 和 >> 运算符，但它无法编译。
The error message is :" error: ‘ostream' does not name a type" Why do I got this error? How to fix it?
错误消息是：“错误：'ostream' 未命名类型” 为什么我会收到此错误？如何解决？
#ifndef COMPLEX_H
#define COMPLEX_H
#include <cstdlib> //exit
#include <istream>
#include <ostream>
class Complex{
public:
Complex(void);
Complex(double a, double b);
Complex(double a);
double real() const{
return a;
}
double imag() const{
return b;
}
friend ostream& operator<<(ostream& out,const Complex& c);
friend istream& operator>>(istream& in, Complex& c);
private:
double a;
double b;
};
ostream& operator<<(ostream& out,const Complex& c){
double a=c.real() , b = c.imag();
out << a << "+" << b<<"i";
return out;
}
istream& operator>>(istream& in, Complex& c){
in >> c.a>> c.b;
return in;
}
#endif
回答by P0W
Use std::ostreamand std::istreameverywhere.
使用std::ostream和std::istream无处不在。
ostreamand istreamare in namespace std
ostream并且istream在命名空间中std
回答by Vlad from Moscow
Us qualified names for types defined in namespace std
命名空间 std 中定义的类型的限定名称
friend std::ostream& operator<<(std::ostream& out,const Complex& c);
It would be also better to include <iostream>instead of two separate headers <istream>and <ostream>
最好包括<iostream>而不是两个单独的标题<istream>和<ostream>
回答by Lucca Psaila
You forgot to add
你忘了添加
using namespace std;
