Using for_each to modify std containers (even though you shouldn't)

Question

I\'m taking a self-study course for C++, learning how the Standard Library works, and I want to understand how this code that uses for_each works, particularly

Answer 1

This is a piece of cake with a lambda expression.

#include 
#include 
#include 
using namespace std;

int main() {
    int mynumbers[] = {8, 9, 7, 6, 4, 1};
    vector s1(mynumbers, mynumbers+6);
    sort(s1.begin(), s1.end());
    for_each(s1.begin(), s1.end(), [](int &x) { x*=2; });
    for_each(s1.begin(), s1.end(), [](int x) { cout << x << ", "; });
    return 0;
}

OUTPUT:
2, 8, 12, 14, 16, 18,