Playing with C++20 concepts

main.cpp

// Try it out on https://godbolt.org/ with Clang with concepts!

// GitHub insists on this having a tab size of 8 even though I told it to use 4, even after deleting and reuploading this. :-(
// Please excuse the massive indents!

#include <iostream>
#include <type_traits>

namespace MyProject {
	template <typename T>
	using Arithmetic = typename std::enable_if<std::is_arithmetic<T>::value, T>::type;

	template<typename T>
	concept ArithmeticConcept = std::is_arithmetic<T>::value;

	template<typename Arithmetic>
	Arithmetic add(Arithmetic a, Arithmetic b) {
		return a + b;
	}

	template<ArithmeticConcept A>
	A addCon(A a, A b) {
		return a + b;
	}
}

int main() {
	using namespace MyProject;
	auto a = add<int>(3, 4);
	auto b = add<double>(3.0, 5.0);
	auto c = add(std::string("blue"), std::string("yellow"));

	std::cout << "Output: " << a << std::endl;
	std::cout << "Output: " << b << std::endl;
	std::cout << "Output: " << c << std::endl;

	auto d = addCon<int>(3, 4);
	auto e = addCon<double>(3.0, 5.0);
	// auto f = addCon<std::string>(std::string("blue"), std::string("yellow"));

	std::cout << "Output: " << d << std::endl;
	std::cout << "Output: " << e << std::endl;
	// std::cout << "Output: " << f << std::endl;

	auto g = add<int>(2, 2);
	auto h = add<long>(2, 2);
	int i = add(2, 2);
	auto j = add(2, 2); // type is inferred from argument types; default here is int
	auto k = add(2ll, 2ll);
	std::cout << "Size of g: " << sizeof(g) << std::endl;
	std::cout << "Size of h: " << sizeof(h) << std::endl;
	std::cout << "Size of i: " << sizeof(i) << std::endl;
	std::cout << "Size of j: " << sizeof(j) << std::endl;
	std::cout << "Size of k: " << sizeof(k) << std::endl;

	return 0;
}