#include <set>
#include <vector>

class A
{
private:
    std::vector<std::set<unsigned, bool(*)(unsigned,unsigned)>> neighbours;
public:
    void run();
};

void A::run()
{
    for (int i = 0; i < 10; ++i)
        neighbours.emplace_back([i](unsigned a, unsigned b){
        // neighbours.emplace_back([](unsigned a, unsigned b){ - with this line instead it compiles
            return a < b;
        });
}

int main()
{
    A a;
    a.run();

    return 0;
}