#include <iostream>
#include <string>
#include <type_traits>

template <typename T>
concept Object = std::is_class_v<T> && requires(T t) {
    { t.toString() } -> std::same_as<std::string>;
};

template <Object O>
void echo(const O o) {
    std::cout << o.toString();
}

template <Object O, Object... Obj>
void echo(const O &o, Obj... obj) {
    std::cout << o.toString();
    echo(obj...);
}

class DataType {
  public:
    DataType(const std::string &n) : name{n} {}
    std::string toString() const { return name + " -> [value of Type]\n"; }

  private:
    std::string name;
};

int main() {
    DataType type1{"hello, "}, type2{"world!"}, type3{" :) "};
    echo(type1, type2, type3);
    // echo(type1, " Hey ", 10); // ERR "Hey" doesn't satisfy requriment
    return 0;
}