Revise the semantics of facade

README.md

@@ -1,4 +1,4 @@
-# Proxy: Polymorphism in C++ Redefined
+# Proxy: Next Generation Polymorphism in C++
 
 [![Proxy-CI](https://github.com/microsoft/proxy/actions/workflows/pipeline-ci.yml/badge.svg)](https://github.com/microsoft/proxy/actions/workflows/pipeline-ci.yml)
 
@@ -24,8 +24,8 @@ The majority of the library is defined in namespace `pro`. Some macros are provi
 // Abstraction (poly is short for polymorphism)
 namespace poly {
 
-PRO_DEF_MEMBER_DISPATCH(Draw, Draw, void(std::ostream&));
-PRO_DEF_MEMBER_DISPATCH(Area, Area, double());
+PRO_DEF_MEMBER_DISPATCH(Draw, void(std::ostream&));
+PRO_DEF_MEMBER_DISPATCH(Area, double());
 PRO_DEF_FACADE(Drawable, PRO_MAKE_DISPATCH_PACK(Draw, Area));
 
 }  // namespace poly
@@ -68,8 +68,7 @@ Here is another demo showing how to define overloads in a dispatch. Note that `.
 // Abstraction (poly is short for polymorphism)
 namespace poly {
 
-PRO_DEF_MEMBER_DISPATCH(Log, Log,
-    void(const char*), void(const char*, const std::exception&));
+PRO_DEF_MEMBER_DISPATCH(Log, void(const char*), void(const char*, const std::exception&));
 PRO_DEF_FACADE(Logger, Log);
 
 }  // namespace poly
@@ -102,6 +101,44 @@ 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.
+
+```cpp
+// Abstraction (poly is short for polymorphism)
+namespace poly {
+
+template <class... Overloads>
+PRO_DEF_FREE_DISPATCH(Call, std::invoke, Overloads...);
+template <class... Overloads>
+PRO_DEF_FACADE(MovableCallable, Call<Overloads...>);
+template <class... Overloads>
+PRO_DEF_FACADE(CopyableCallable, Call<Overloads...>, pro::copyable_pointer_constraints);
+
+}  // namespace poly
+
+// MyFunction has similar functionality as std::function but supports multiple overloads
+// MyMoveOnlyFunction has similar functionality as std::move_only_function but supports multiple overloads
+template <class... Overloads>
+using MyFunction = pro::proxy<poly::MovableCallable<Overloads...>>;
+template <class... Overloads>
+using MyMoveOnlyFunction = pro::proxy<poly::CopyableCallable<Overloads...>>;
+
+int main() {
+  auto f = [](auto&&... v) {
+    printf("f() called. Args: ");
+    ((std::cout << v << ":" << typeid(decltype(v)).name() << ", "), ...);
+    puts("");
+  };
+  MyFunction<void(int)> p0{&f};
+  p0(123);  // Prints "f() called. Args: 123:i," (assuming GCC)
+  MyMoveOnlyFunction<void(), void(int), void(double)> p1{&f};
+  p1();  // Prints "f() called. Args:"
+  p1(456);  // Prints "f() called. Args: 456:i,"
+  p1(1.2);  // Prints "f() called. Args: 1.2:d,"
+  return 0;
+}
+```
+
 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/5a3jeE1M8)).
 
 ## Minimum requirements for compilers

proxy.h

@@ -601,15 +601,15 @@ struct facade_prototype {
 
 }  // namespace pro
 
-#define PRO_DEF_MEMBER_DISPATCH(__NAME, __FUNC, ...) \
+#define PRO_DEF_MEMBER_DISPATCH(__NAME, ...) \
     struct __NAME { \
       using overload_types = std::tuple<__VA_ARGS__>;\
       template <class __T, class... __Args> \
       decltype(auto) operator()(__T&& __self, __Args&&... __args) \
           requires(requires{ std::forward<__T>(__self) \
-              .__FUNC(std::forward<__Args>(__args)...); }) { \
+              .__NAME(std::forward<__Args>(__args)...); }) { \
         return std::forward<__T>(__self) \
-            .__FUNC(std::forward<__Args>(__args)...); \
+            .__NAME(std::forward<__Args>(__args)...); \
       } \
     }
 #define PRO_DEF_FREE_DISPATCH(__NAME, __FUNC, ...) \

samples/resource_dictionary/main.cpp

@@ -7,8 +7,8 @@
 
 namespace poly {
 
-PRO_DEF_MEMBER_DISPATCH(At, at, std::string(int));
-PRO_DEF_FACADE(Dictionary, At);
+PRO_DEF_MEMBER_DISPATCH(at, std::string(int));
+PRO_DEF_FACADE(Dictionary, at);
 
 }  // namespace poly
 

tests/proxy_integration_tests.cpp

@@ -15,8 +15,8 @@ namespace {
 
 namespace poly {
 
-PRO_DEF_MEMBER_DISPATCH(Draw, Draw, void(std::ostream&));
-PRO_DEF_MEMBER_DISPATCH(Area, Area, double());
+PRO_DEF_MEMBER_DISPATCH(Draw, void(std::ostream&));
+PRO_DEF_MEMBER_DISPATCH(Area, double());
 PRO_DEF_FACADE(Drawable, PRO_MAKE_DISPATCH_PACK(Draw, Area));
 
 }  // namespace poly

tests/proxy_invocation_tests.cpp

@@ -16,7 +16,7 @@ namespace {
 namespace poly {
 
 template <class... Os>
-PRO_DEF_MEMBER_DISPATCH(Call, operator(), Os...);
+PRO_DEF_FREE_DISPATCH(Call, std::invoke, Os...);
 template <class... Os>
 PRO_DEF_FACADE(Callable, Call<Os...>, pro::copyable_pointer_constraints);