a1/hello-cpp20.cc


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import <iostream>;
import <string>;

template<typename T>
concept Printable = requires(T a) { std::cout << a; };

void printIt(const Printable auto& p)
{
	std::cout << p;
}

struct MyType {};

int main()
{
	using namespace std::string_literals;
	printIt("Hello Modern World!\n"); // ok, const char* string is printable
	printIt("Hello Modern World!\n"s); // ok, std::string literal is printable
	printIt(42); // ok, int is printable
	// printIt(MyType{}); // error: doesn't adhere to Printable concept
}