Update documentation of ex1

Author: juzzlin

src/examples/ex1/ex1.cpp

@@ -29,29 +29,40 @@
 
 using juzzlin::Argengine;
 
+//
+// Ex1: Demonstrate basic usage.
+//
+
 int main(int argc, char ** argv)
 {
+    // Instantiate Argengine and give it the raw argument data.
     Argengine ae(argc, argv);
+
+    // Add option "-a" that, when set, prints all arguments given to the binary.
     ae.addOption(
       { "-a", "--arguments" }, [&] {
           for (int i = 0; i < argc; i++) {
               std::cout << argv[i] << std::endl;
           }
       },
-      false, "Print arguments.");
+      false, "Print arguments."); // Set the option non-required and set documentation string.
+
+    // Add option "-p" that prints the length of the given string e.g. "-p FOO".
     ae.addOption(
       { "-p" }, [](std::string value) {
           std::cout << value.size() << std::endl;
       },
-      true, "Print length of given text. This option is required.", "TEXT");
+      true, "Print length of given text. This option is required.", "TEXT"); // Set the option required and set documentation string and variable name shown in the documentation.
 
+    // Parse the arguments and store possible error to variable error.
     Argengine::Error error;
     ae.parse(error);
 
+    // Check error and print the possible error message.
     if (error.code != Argengine::Error::Code::Ok) {
         std::cerr << error.message << std::endl
                   << std::endl;
-        ae.printHelp();
+        ae.printHelp(); // Print the auto-generated help.
         return EXIT_FAILURE;
     }