http://aherrmann.github.io/programming/2014/10/19/type-erasure-with-merged-concepts/

type_erasure.cpp

#include <iostream>
#include <memory>
#include <string>

class Greeter {
  public:
    template <class T>
    Greeter(T data) : self_(std::make_shared<Model<T>>(data)) {}

    void greet(const std::string &name) const {
        self_->greet(name);
    }

  private:
    struct Concept {
        virtual ~Concept() = default;
        virtual void greet(const std::string &) const = 0;
    };
    template <class T>
    class Model : public Concept {
      public:
        Model(T data) : data_(data) {}
        virtual void greet(const std::string &name) const override {
            data_.greet(name);
        }

      private:
        T data_;
    };

    std::shared_ptr<const Concept> self_;
};

class English {
  public:
    void greet(const std::string &name) const {
        std::cout << "Good day " << name << ". How are you?\n";
    }
};

class French {
  public:
    void greet(const std::string &name) const {
        std::cout << "Bonjour " << name << ". Comment ca va?\n";
    }
};

void greet_tom(const Greeter &g) {
    g.greet("Tom");
}

int main() {
    greet_tom(English{});
    greet_tom(French{});
}