#include <iostream>
#include <vector>
#include <algorithm>
class MyData
    {
    public:
        int m_iData;
        bool operator<(MyData rhs) { return m_iData < rhs.m_iData; }
    };
 
int main () 
{
    std:: vector <MyData> myvector(2,MyData() );
    myvector[0].m_iData=2; myvector[1].m_iData=4;
 
    std::sort(myvector.begin(),myvector.end()); 
}

试图编译这个给出：

error: passing 'const MyData' as 'this' argument of 'bool MyData::operator<(MyData)'
discards qualifiers