Static polymorphism with c++20 concepts

static-polymorphism.cc

// Core C++ 2021 :: C++ 20 Overview: The Big Four
// https://youtu.be/emcC_Cv8EpQ

#include <iostream>
#include <tuple>

template <typename T>
concept Drawable = requires(T s) {
    s.draw();
};

class Rectangle {
   public:
    auto draw() const { std::cout << "Draw an rectangle!\n"; }
};

class Circle {
   public:
    auto draw() const { std::cout << "Draw a circle!\n"; }
};

class Square {
   public:
    auto draw() const { std::cout << "Draw a square!\n"; }
};

template <size_t Index = 0, Drawable... Ts>
constexpr auto drawAll(const std::tuple<Ts...>& shapes) {
    if constexpr (Index != sizeof...(Ts)) {
	std::get<Index>(shapes).draw();
	drawAll<Index + 1>(shapes);
    }
}

int main() { 
	drawAll(std::make_tuple(Rectangle{}, Circle{}, Square{})); 
}