C++ 错误 具有类型“const sort”的表达式会丢失一些 const-volatile 限定符以调用“bool sort::operator ()(int,int)” 如下：环境 vs2019 内容：set内置函数排序

C++ 错误 具有类型“const sort”的表达式会丢失一些 const-volatile 限定符以调用“bool sort::operator ()(int,int)”  如下：

环境 vs2019

内容：set内置函数排序 

 

 

 

#include <iostream>
#include<set>
#include<string>

using namespace std;


class sort
{
public:
    bool operator()(int v1, int v2) 
    {
        return v1 > v2;
    }
};


void test01()
{
    set<int>s1;
    s1.insert(30);
    s1.insert(10);
    s1.insert(50);
    s1.insert(20);
    s1.insert(40);

    for (set<int>::iterator it = s1.begin(); it != s1.end(); it++)
    {
        cout << *it << " ";
    }
    cout << endl;

    set<int, sort>s2;
    s2.insert(30);
    s2.insert(10);
    s2.insert(50);
    s2.insert(20);
    s2.insert(40);

    for (set<int, sort>::iterator it = s2.begin(); it != s2.end(); it++)
    {
        cout << *it << " ";
    }
    cout << endl;


}
int main()
{

    test01();

    system("pause");
    return 0;
}

//改正   在仿函数中加入const

#include <iostream>
#include<set>
#include<string>

using namespace std;


class sort
{
public:
    bool operator()(int v1, int v2) const
    {
        return v1 > v2;
    }
};


void test01()
{
    set<int>s1;
    s1.insert(30);
    s1.insert(10);
    s1.insert(50);
    s1.insert(20);
    s1.insert(40);

    for (set<int>::iterator it = s1.begin(); it != s1.end(); it++)
    {
        cout << *it << " ";
    }
    cout << endl;

    set<int, sort>s2;
    s2.insert(30);
    s2.insert(10);
    s2.insert(50);
    s2.insert(20);
    s2.insert(40);

    for (set<int, sort>::iterator it = s2.begin(); it != s2.end(); it++)
    {
        cout << *it << " ";
    }
    cout << endl;


}
int main()
{

    test01();

    system("pause");
    return 0;
}