Fix readme and refactor sample code (#94)

README.md

@@ -48,8 +48,8 @@ class Rectangle {
 std::string PrintDrawableToString(pro::proxy<spec::Drawable> p) {
   std::stringstream result;
   result << "shape = ";
-  p.Draw(result);
-  result << ", area = " << p.Area();
+  p.Draw(result);  // Polymorphic call
+  result << ", area = " << p.Area();  // Polymorphic call
   return std::move(result).str();
 }
 
@@ -62,7 +62,7 @@ pro::proxy<spec::Drawable> CreateRectangleAsDrawable(int width, int height) {
 }
 ```
 
-Here is another demo showing how to define overloads in a dispatch. Note that `.invoke<>` can be ommitted when only 1 dispatch is defined in a facade:
+Here is another demo showing how to define overloads in a dispatch: just to add any number of signatures in the definition of a dispatch.
 
 ```cpp
 // Specifications of abstraction
@@ -75,11 +75,11 @@ PRO_DEF_FACADE(Logger, Log);
 
 // Client - Consumer
 void MyVerboseFunction(pro::proxy<spec::Logger> logger) {
-  logger("hello");
+  logger.Log("hello");
   try {
     throw std::runtime_error{"runtime error!"};
   } catch (const std::exception& e) {
-    logger("world", e);
+    logger.Log("world", e);
   }
 }
 
@@ -101,7 +101,7 @@ int main() {
 }
 ```
 
-By design, the body of a dispatch could be any code. While member function is one useful pattern supported by macro `PRO_DEF_MEMBER_DISPATCH`, free function is also supported with another macro `PRO_DEF_FREE_DISPATCH`. The following example uses `PRO_DEF_FREE_DISPATCH` and `std::invoke` to implement similar function wrapper as `std::function` and `std::move_only_function` and supports multiple overloads.
+By design, the body of a dispatch could be any code. While member function is one useful pattern supported by macro `PRO_DEF_MEMBER_DISPATCH`, free function is also supported with another macro `PRO_DEF_FREE_DISPATCH`. The following example uses `PRO_DEF_FREE_DISPATCH` and `std::invoke` to implement similar function wrapper as `std::function` and `std::move_only_function` and supports multiple overloads.  Note that `.Call` can be omitted when only 1 dispatch is defined in a facade:
 
 ```cpp
 // Specifications of abstraction
@@ -139,7 +139,7 @@ int main() {
 }
 ```
 
-Please find more details and discussions in the spec. The complete version of the "drawable" demo could be found in [tests/proxy_integration_tests.cpp](tests/proxy_integration_tests.cpp) (also available on [Compiler Explorer](https://godbolt.org/z/voEacxT76)).
+Please find more details and discussions in the spec. The complete version of the "drawable" demo could be found in [tests/proxy_integration_tests.cpp](tests/proxy_integration_tests.cpp) (also available on [Compiler Explorer](https://godbolt.org/z/4cK8PPTE1)).
 
 ## Minimum requirements for compilers
 

tests/proxy_integration_tests.cpp

@@ -23,10 +23,10 @@ PRO_DEF_FACADE(Drawable, PRO_MAKE_DISPATCH_PACK(Draw, Area));
 
 class Rectangle {
  public:
+  explicit Rectangle(double width, double height) : width_(width), height_(height) {}
+  Rectangle(const Rectangle&) = default;
   void Draw(std::ostream& out) const
       { out << "{Rectangle: width = " << width_ << ", height = " << height_ << "}"; }
-  void SetWidth(double width) { width_ = width; }
-  void SetHeight(double height) { height_ = height; }
   double Area() const noexcept { return width_ * height_; }
 
  private:
@@ -36,8 +36,9 @@ class Rectangle {
 
 class Circle {
  public:
+  explicit Circle(double radius) : radius_(radius) {}
+  Circle(const Circle&) = default;
   void Draw(std::ostream& out) const { out << "{Circle: radius = " << radius_ << "}"; }
-  void SetRadius(double radius) { radius_ = radius; }
   double Area() const noexcept { return std::numbers::pi * radius_ * radius_; }
 
  private:
@@ -88,18 +89,11 @@ pro::proxy<spec::Drawable> MakeDrawableFromCommand(const std::string& s) {
       if (parsed.size() == 3u) {
         static std::pmr::unsynchronized_pool_resource rectangle_memory_pool;
         std::pmr::polymorphic_allocator<> alloc{&rectangle_memory_pool};
-        auto deleter = [alloc](Rectangle* ptr) mutable
-            { alloc.delete_object<Rectangle>(ptr); };
-        Rectangle* instance = alloc.new_object<Rectangle>();
-        std::unique_ptr<Rectangle, decltype(deleter)> p{instance, deleter};
-        p->SetWidth(std::stod(parsed[1u]));
-        p->SetHeight(std::stod(parsed[2u]));
-        return p;
+        return pro::allocate_proxy<spec::Drawable, Rectangle>(alloc, std::stod(parsed[1u]), std::stod(parsed[2u]));
       }
     } else if (parsed[0u] == "Circle") {
       if (parsed.size() == 2u) {
-        Circle circle;
-        circle.SetRadius(std::stod(parsed[1u]));
+        Circle circle{std::stod(parsed[1u])};
         return pro::make_proxy<spec::Drawable>(circle);
       }
     } else if (parsed[0u] == "Point") {