I can answer both questions with a sprinkle of template magic:

    #include <iostream>
    #include <functional>

    template <typename Ret, typename First, typename ...Rest>
    class Curry {
        std::function<Ret(First, Rest...)> fn;
      public:
        Curry(std::function<Ret(First, Rest...)> fn): fn(fn) {};
        Curry<Ret, Rest...> operator()(First arg) {
            return Curry<Ret, Rest...>{[this, arg](Rest... args) {
                return this->fn(arg, args...);
            }};
        }
    };

    template <typename Ret, typename Arg>
    class Curry<Ret, Arg> {
        std::function<Ret(Arg)> fn;
      public:
        Curry(std::function<Ret(Arg)> fn): fn(fn) {};
        Ret operator()(Arg arg) {
            return this->fn(arg);
        }
    };


    int uncurried(int a, int b, int c) {
        return a + 2*b + 3*c;
    }

    int main() {
        auto curried = Curry<int, int, int, int>{uncurried};

        std::cout << curried(1)(2)(3) << std::endl;
    }