Add some more basic examples to thread.cpp

thread.cpp

 #include <thread>
 #include <iostream>
 
-void thread_method() {
-    std::cout << "hello thread" << std::endl;
+void thread_method(int i) {
+    std::cout << "hello thread " << i << std::endl;
 }
 
+struct ThreadObject {
+    void operator()(int i) const {
+        std::cout << "hello object " << i << std::endl;
+    }
+};
+
 int main() {
-    std::thread thread(thread_method);
-    thread.join();
+    // Note that no care is taken to avoid race conditions around the global object std::cout.
+    // Arguments are copied into the child threads.
+    auto function_thread = std::thread(thread_method, 1);
+    auto object_thread = std::thread(ThreadObject(), 2);
+    auto lambda_thread = std::thread([](int i) {
+        std::cout << "hello lambda " << i << std::endl;
+    }, 3);
+
+    // Without these, the main thread could terminate before the children complete.
+    function_thread.join();
+    object_thread.join();
+    lambda_thread.join();
+
     return 0;
 }