int src[] = {1,2,3,4,5,6,7,8};
auto dst = from(src).where( [](int a) { return a % 2 == 1; })      // 1,3,5,7
                    .select([](int a) { return a * 2; })           // 2,6,10,14
                    .where( [](int a) { return a > 2 && a < 12; }) // 6,10
                    .toStdVector();

// dst type: std::vector<int>
// dst items: 6,10

struct Man {
    std::string name;
    int age;
};

Man src[] = {
    {"Kevin",14},
    {"Anton",18},
    {"Agata",17},
    {"Terra",20},
    {"Layer",15},
};

auto dst = from(src).where(  [](const Man & man) { return man.age < 18; })
                    .orderBy([](const Man & man) { return man.age; })
                    .select( [](const Man & man) { return man.name; })
                    .toStdVector();

// dst type: std::vector<std::string>
// dst items: "Kevin", "Layer", "Agata"

struct Message {
    std::string PhoneA;
    std::string PhoneB;
    std::string Text;
};

Message messages[] = {
    {"Anton","Troll","Hello, friend!"},
    {"Denis","Wride","OLOLO"},
    {"Anton","Papay","WTF?"},
    {"Denis","Maloy","How r u?"},
    {"Denis","Wride","Param-pareram!"},
};

int DenisUniqueContactCount =
    from(messages).where(   [](const Message & msg) { return msg.PhoneA == "Denis"; })
                  .distinct([](const Message & msg) { return msg.PhoneB; })
                  .count();

// DenisUniqueContactCount == 2