Add folder test_your_setup

test_your_setup/README.md

+# Compile:
+
+## hello.cc
+g++ hello.cc
+clang++ hello.cc
+
+## hello_c++20.cc
+g++ -std=c++20 hello_c++20.cc 
+clang++ -std=c++20 -stdlib=libc++ hello_c++20.cc 
+
+## hello_m.cc
+
+With gcc:
+g++ -std=c++20 -fmodules-ts -xc++-system-header iostream
+g++ -std=c++20 -fmodules-ts hello_m.cc
+
+with clang:
+clang++ -std=c++20 -stdlib=libc++ -fmodules hello_m.cc
+
+## hello_c++20_m.cc
+
+With gcc:
+g++ -std=c++20 -fmodules-ts -xc++-system-header concepts
+g++ -std=c++20 -fmodules-ts -xc++-system-header iostream
+g++ -std=c++20 -fmodules-ts hello_c++20_m.cc
+
+With clang:
+clang++ -std=c++20 -stdlib=libc++ -fmodules hello_c++20_m.cc
+
+

test_your_setup/hello.cc

+#include <iostream>
+
+auto main() -> int
+{
+    std::cout << "Hello, world!\n";
+}

test_your_setup/hello_c++20.cc

+#include <iostream>
+#include <concepts>
+
+auto message(auto&& x)
+{
+    std::cout << x << "\n";
+}
+
+template <class T>
+concept is_a_number = std::integral<T> or std::floating_point<T>;
+
+auto main() -> int
+{
+    message("Hello, world!");
+    auto n = 1234.0;
+    if constexpr (is_a_number<decltype(n)>)
+	std::cout << n << " is a number.\n";
+    else
+	std::cout << n << " is not a number!\n";
+}
+

test_your_setup/hello_c++20_m.cc

+import <iostream>;
+import <concepts>;
+
+auto message(auto&& x)
+{
+    std::cout << x << "\n";
+}
+
+template <class T>
+concept is_a_number = std::integral<T> or std::floating_point<T>;
+
+auto main() -> int
+{
+    message("Hello, world!");
+    auto n = 1234.0;
+    if constexpr (is_a_number<decltype(n)>)
+	std::cout << n << " is a number.\n";
+    else
+	std::cout << n << " is not a number!\n";
+}
+

test_your_setup/hello_m.cc

+import <iostream>;
+
+auto main() -> int
+{
+    std::cout << "Hello, world!\n";
+}
+