How to sort a vector containing const values

Question

I have a vector set up like this and I want to sort it:

#include <iostream>
#include <vector>
#include <algorithm> 

using namespace std;

int main()
{
    const int a =10;
    int b = 20;
    pair<const int, int> constPair1(a,b);
    b=30;
    pair<const int, int> constPair2(a,b);
    vector<pair<const int, int>> vec{constPair1,constPair2};
    sort(vec.begin(),vec.end());

    return 0;
}

Unfortunately the sort above will not compile because of the const values. Is there any way I can sort this vector? Or am I stuck creating a new vector and copying values over?

Answer 1

In C++03, elements in a std::vector have to be copy-assignable and copy-constructible in c++. A pair with a const member does not meet that requirement and is thus invalid. The compiler is right to recject it.

In C++11, elements in a std::vector have to be move-assignable and move-constructible. A pair with a const member cannot be moved and will thus result in invalid code.