#include <list>
#include <iostream>
 
int main() {
    typedef void linearVariable;  // Dummy to make the code compile.
    typedef std::pair<linearVariable*, double> weightedVariable;
    std::list<weightedVariable> tmp;
 
    tmp.emplace_back(std::make_pair(nullptr, 0.4));
    tmp.emplace_back(std::make_pair(nullptr, 0.8));
    tmp.emplace_back(std::make_pair(nullptr, 0.2));
 
    tmp.sort([](const weightedVariable& a, const weightedVariable& b) {
        return a.second < b.second;
    });
 
    for (auto const &wv : tmp)
        std::cout << wv.second << std::endl;
 
    return 0;
}

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