[英]Overloading less than operator
I am overloading a less than operator for a class like so: 我正在为一个像这样的类重载一个小于运算符:
#include<string>
using namespace std;
class X{
public:
X(long a, string b, int c);
friend bool operator< (X& a, X& b);
private:
long a;
string b;
int c;
};
and then the implementation file: 然后执行文件:
#include "X.h"
bool operator < (X const& lhs, X const& rhs)
{
return lhs.a< rhs.a;
}
However it is not letting me access the a
data member in the implementation file because a
is declared as a private data member, even though its through an X
object? 但是它不允许我访问实现文件中
a
数据成员,因为a
被声明为私有数据成员,即使它是通过X
对象?
The friend function does not have the same signature as the function defined function: friend函数与函数定义函数的签名不同:
friend bool operator< (X& a, X& b);
and 和
bool operator < (X const& lhs, X const& rhs)
// ^^^^^ ^^^^^
You should just change the line in your header file to: 您只需将头文件中的行更改为:
friend bool operator< ( X const& a, X const& b);
// ^^^^^ ^^^^^
As you don't modify the objects inside the comparison operators, they should take const-references. 由于您不修改比较运算符内的对象,因此它们应该采用const引用。
You have declared a different friend function to the one you are trying to use. 您已声明了与您尝试使用的功能不同的朋友功能。 You need
你需要
friend bool operator< (const X& a, const X& b);
// ^^^^^ ^^^^^
In any case, it would make no sense for a comparison operator to take non-const references. 无论如何,比较运算符采用非const引用是没有意义的。
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