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


int main(void)
{
    std::vector<int> foo = {25, 15, 5, -5, -15};
    std::vector<int > bar(foo.size());

    auto it = std::copy_if(foo.begin(), foo.end(), bar.begin(), [](int i){ return !(i < 0); });
    bar.resize(std::distance(bar.begin(), it)); //shrink container to new size
    std::cout << "bar constains:";
    for(int &x : bar) std::cout << " " << x;
    std::cout << "\n";
}