Release 1.52.0

[SVN r81201]

include/boost/detail/call_traits.hpp

@@ -24,6 +24,7 @@
 #include <cstddef>
 
 #include <boost/type_traits/is_arithmetic.hpp>
+#include <boost/type_traits/is_enum.hpp>
 #include <boost/type_traits/is_pointer.hpp>
 #include <boost/detail/workaround.hpp>
 
@@ -43,20 +44,26 @@ struct ct_imp2<T, true>
    typedef const T param_type;
 };
 
-template <typename T, bool isp, bool b1>
+template <typename T, bool isp, bool b1, bool b2>
 struct ct_imp
 {
    typedef const T& param_type;
 };
 
-template <typename T, bool isp>
-struct ct_imp<T, isp, true>
+template <typename T, bool isp, bool b2>
+struct ct_imp<T, isp, true, b2>
 {
    typedef typename ct_imp2<T, sizeof(T) <= sizeof(void*)>::param_type param_type;
 };
 
-template <typename T, bool b1>
-struct ct_imp<T, true, b1>
+template <typename T, bool isp, bool b1>
+struct ct_imp<T, isp, b1, true>
+{
+   typedef typename ct_imp2<T, sizeof(T) <= sizeof(void*)>::param_type param_type;
+};
+
+template <typename T, bool b1, bool b2>
+struct ct_imp<T, true, b1, b2>
 {
    typedef const T param_type;
 };
@@ -79,7 +86,8 @@ public:
    typedef typename boost::detail::ct_imp<
       T,
       ::boost::is_pointer<T>::value,
-      ::boost::is_arithmetic<T>::value
+      ::boost::is_arithmetic<T>::value,
+      ::boost::is_enum<T>::value
    >::param_type param_type;
 };
 

include/boost/utility/detail/result_of_iterate.hpp

@@ -5,6 +5,11 @@
 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
 //  http://www.boost.org/LICENSE_1_0.txt)
 
+//  Copyright Daniel Walker, Eric Niebler, Michel Morin 2008-2012.
+//  Use, modification and distribution is subject to the Boost Software
+//  License, Version 1.0. (See accompanying file LICENSE_1_0.txt or
+//  copy at http://www.boost.org/LICENSE_1_0.txt)
+
 // For more information, see http://www.boost.org/libs/utility
 #if !defined(BOOST_PP_IS_ITERATING)
 # error Boost result_of - do not include this file!
@@ -18,31 +23,29 @@
 #endif
 
 #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
-template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of<F(BOOST_RESULT_OF_ARGS)>
     : mpl::if_<
           mpl::or_< is_pointer<F>, is_member_function_pointer<F> >
         , boost::detail::tr1_result_of_impl<
-            typename remove_cv<F>::type, 
-            typename remove_cv<F>::type(BOOST_RESULT_OF_ARGS), 
+            typename remove_cv<F>::type,
+            typename remove_cv<F>::type(BOOST_RESULT_OF_ARGS),
             (boost::detail::has_result_type<F>::value)>
         , boost::detail::tr1_result_of_impl<
             F,
-            F(BOOST_RESULT_OF_ARGS), 
+            F(BOOST_RESULT_OF_ARGS),
             (boost::detail::has_result_type<F>::value)> >::type { };
 #endif
 
-#if !defined(BOOST_NO_DECLTYPE) && defined(BOOST_RESULT_OF_USE_DECLTYPE)
+#ifdef BOOST_RESULT_OF_USE_DECLTYPE
 
 // Uses declval following N3225 20.7.7.6 when F is not a pointer.
-template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct result_of<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
     : mpl::if_<
-          mpl::or_< is_pointer<F>, is_member_function_pointer<F> >
+          is_member_function_pointer<F>
         , detail::tr1_result_of_impl<
-            typename remove_cv<F>::type, 
+            typename remove_cv<F>::type,
             typename remove_cv<F>::type(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), false
           >
         , detail::cpp0x_result_of_impl<
@@ -53,53 +56,119 @@ struct result_of<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
 
 namespace detail {
 
-template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
-struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T))>
+#ifdef BOOST_NO_SFINAE_EXPR
+
+template<typename F>
+struct BOOST_PP_CAT(result_of_callable_fun_2_, BOOST_PP_ITERATION());
+
+template<typename R BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(), typename T)>
+struct BOOST_PP_CAT(result_of_callable_fun_2_, BOOST_PP_ITERATION())<R(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(), T))> {
+    R operator()(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(), T)) const;
+    typedef result_of_private_type const &(*pfn_t)(...);
+    operator pfn_t() const volatile;
+};
+
+template<typename F>
+struct BOOST_PP_CAT(result_of_callable_fun_, BOOST_PP_ITERATION());
+
+template<typename F>
+struct BOOST_PP_CAT(result_of_callable_fun_, BOOST_PP_ITERATION())<F *>
+  : BOOST_PP_CAT(result_of_callable_fun_2_, BOOST_PP_ITERATION())<F>
+{};
+
+template<typename F>
+struct BOOST_PP_CAT(result_of_callable_fun_, BOOST_PP_ITERATION())<F &>
+  : BOOST_PP_CAT(result_of_callable_fun_2_, BOOST_PP_ITERATION())<F>
+{};
+
+template<typename F>
+struct BOOST_PP_CAT(result_of_select_call_wrapper_type_, BOOST_PP_ITERATION())
+  : mpl::eval_if<
+        is_class<typename remove_reference<F>::type>,
+        result_of_wrap_callable_class<F>,
+        mpl::identity<BOOST_PP_CAT(result_of_callable_fun_, BOOST_PP_ITERATION())<typename remove_cv<F>::type> >
+    >
+{};
+
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(), typename T)>
+struct BOOST_PP_CAT(result_of_is_callable_, BOOST_PP_ITERATION()) {
+    typedef typename BOOST_PP_CAT(result_of_select_call_wrapper_type_, BOOST_PP_ITERATION())<F>::type wrapper_t;
+    static const bool value = (
+        sizeof(result_of_no_type) == sizeof(detail::result_of_is_private_type(
+            (boost::declval<wrapper_t>()(BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)), result_of_weird_type())
+        ))
+    );
+    typedef mpl::bool_<value> type;
+};
+
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
+struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), true>
+    : lazy_enable_if<
+          BOOST_PP_CAT(result_of_is_callable_, BOOST_PP_ITERATION())<F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(), T)>
+        , cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), false>
+      >
+{};
+
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
+struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), false>
 {
   typedef decltype(
     boost::declval<F>()(
-      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), declval<T, >() BOOST_PP_INTERCEPT)
+      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
     )
   ) type;
 };
 
-} // namespace detail 
+#else // BOOST_NO_SFINAE_EXPR
 
-#else // defined(BOOST_NO_DECLTYPE)
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
+struct cpp0x_result_of_impl<F(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)),
+                            typename result_of_always_void<decltype(
+                                boost::declval<F>()(
+                                    BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
+                                )
+                            )>::type> {
+  typedef decltype(
+    boost::declval<F>()(
+      BOOST_PP_ENUM_BINARY_PARAMS(BOOST_PP_ITERATION(), boost::declval<T, >() BOOST_PP_INTERCEPT)
+    )
+  ) type;
+};
+
+#endif // BOOST_NO_SFINAE_EXPR
+
+} // namespace detail
+
+#else // defined(BOOST_RESULT_OF_USE_DECLTYPE)
 
 #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
-template<typename F BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename F BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct result_of<F(BOOST_RESULT_OF_ARGS)>
     : tr1_result_of<F(BOOST_RESULT_OF_ARGS)> { };
 #endif
 
-#endif // defined(BOOST_NO_DECLTYPE)
+#endif // defined(BOOST_RESULT_OF_USE_DECLTYPE)
 
 #undef BOOST_RESULT_OF_ARGS
 
-#if BOOST_PP_ITERATION() >= 1 
+#if BOOST_PP_ITERATION() >= 1
 
 namespace detail {
 
-template<typename R,  typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R,  typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (*)(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), FArgs, false>
 {
   typedef R type;
 };
 
-template<typename R,  typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R,  typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (&)(BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),T)), FArgs, false>
 {
   typedef R type;
 };
 
 #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
-template<typename R, typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R, typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (T0::*)
                      (BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_PP_ITERATION(),T)),
                  FArgs, false>
@@ -107,8 +176,7 @@ struct tr1_result_of_impl<R (T0::*)
   typedef R type;
 };
 
-template<typename R, typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R, typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (T0::*)
                      (BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_PP_ITERATION(),T))
                      const,
@@ -117,8 +185,7 @@ struct tr1_result_of_impl<R (T0::*)
   typedef R type;
 };
 
-template<typename R, typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R, typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (T0::*)
                      (BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_PP_ITERATION(),T))
                      volatile,
@@ -127,8 +194,7 @@ struct tr1_result_of_impl<R (T0::*)
   typedef R type;
 };
 
-template<typename R, typename FArgs BOOST_PP_COMMA_IF(BOOST_PP_ITERATION())
-         BOOST_PP_ENUM_PARAMS(BOOST_PP_ITERATION(),typename T)>
+template<typename R, typename FArgs BOOST_PP_ENUM_TRAILING_PARAMS(BOOST_PP_ITERATION(),typename T)>
 struct tr1_result_of_impl<R (T0::*)
                      (BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_PP_ITERATION(),T))
                      const volatile,

include/boost/utility/result_of.hpp

@@ -10,24 +10,48 @@
 #define BOOST_RESULT_OF_HPP
 
 #include <boost/config.hpp>
-#include <boost/preprocessor/iteration/iterate.hpp> 
-#include <boost/preprocessor/punctuation/comma_if.hpp> 
-#include <boost/preprocessor/repetition/enum_params.hpp> 
-#include <boost/preprocessor/repetition/enum_binary_params.hpp> 
-#include <boost/preprocessor/repetition/enum_shifted_params.hpp> 
-#include <boost/preprocessor/facilities/intercept.hpp> 
+#include <boost/preprocessor/cat.hpp>
+#include <boost/preprocessor/iteration/iterate.hpp>
+#include <boost/preprocessor/repetition/enum_params.hpp>
+#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
+#include <boost/preprocessor/repetition/enum_binary_params.hpp>
+#include <boost/preprocessor/repetition/enum_shifted_params.hpp>
+#include <boost/preprocessor/facilities/intercept.hpp>
 #include <boost/detail/workaround.hpp>
 #include <boost/mpl/has_xxx.hpp>
 #include <boost/mpl/if.hpp>
+#include <boost/mpl/eval_if.hpp>
 #include <boost/mpl/bool.hpp>
+#include <boost/mpl/identity.hpp>
 #include <boost/mpl/or.hpp>
+#include <boost/type_traits/is_class.hpp>
 #include <boost/type_traits/is_pointer.hpp>
 #include <boost/type_traits/is_member_function_pointer.hpp>
 #include <boost/type_traits/remove_cv.hpp>
+#include <boost/type_traits/remove_reference.hpp>
 #include <boost/utility/declval.hpp>
+#include <boost/utility/enable_if.hpp>
 
 #ifndef BOOST_RESULT_OF_NUM_ARGS
-#  define BOOST_RESULT_OF_NUM_ARGS 10
+#  define BOOST_RESULT_OF_NUM_ARGS 16
+#endif
+
+// Use the decltype-based version of result_of by default if the compiler
+// supports N3276 <http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2011/n3276.pdf>.
+// The user can force the choice by defining either BOOST_RESULT_OF_USE_DECLTYPE or
+// BOOST_RESULT_OF_USE_TR1, but not both!
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE) && defined(BOOST_RESULT_OF_USE_TR1)
+#  error Both BOOST_RESULT_OF_USE_DECLTYPE and BOOST_RESULT_OF_USE_TR1 cannot be defined at the same time.
+#endif
+
+#ifndef BOOST_RESULT_OF_USE_TR1
+#  ifndef BOOST_RESULT_OF_USE_DECLTYPE
+#    ifndef BOOST_NO_DECLTYPE_N3276 // this implies !defined(BOOST_NO_DECLTYPE)
+#      define BOOST_RESULT_OF_USE_DECLTYPE
+#    else
+#      define BOOST_RESULT_OF_USE_TR1
+#    endif
+#  endif
 #endif
 
 namespace boost {
@@ -41,7 +65,67 @@ namespace detail {
 BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
 
 template<typename F, typename FArgs, bool HasResultType> struct tr1_result_of_impl;
-template<typename F> struct cpp0x_result_of_impl;
+
+#ifdef BOOST_NO_SFINAE_EXPR
+
+struct result_of_private_type {};
+
+struct result_of_weird_type {
+  friend result_of_private_type operator,(result_of_private_type, result_of_weird_type);
+};
+
+typedef char result_of_yes_type;      // sizeof(result_of_yes_type) == 1
+typedef char (&result_of_no_type)[2]; // sizeof(result_of_no_type)  == 2
+
+template<typename T>
+result_of_no_type result_of_is_private_type(T const &);
+result_of_yes_type result_of_is_private_type(result_of_private_type);
+
+template<typename C>
+struct result_of_callable_class : C {
+    result_of_callable_class();
+    typedef result_of_private_type const &(*pfn_t)(...);
+    operator pfn_t() const volatile;
+};
+
+template<typename C>
+struct result_of_wrap_callable_class {
+  typedef result_of_callable_class<C> type;
+};
+
+template<typename C>
+struct result_of_wrap_callable_class<C const> {
+  typedef result_of_callable_class<C> const type;
+};
+
+template<typename C>
+struct result_of_wrap_callable_class<C volatile> {
+  typedef result_of_callable_class<C> volatile type;
+};
+
+template<typename C>
+struct result_of_wrap_callable_class<C const volatile> {
+  typedef result_of_callable_class<C> const volatile type;
+};
+
+template<typename C>
+struct result_of_wrap_callable_class<C &> {
+  typedef typename result_of_wrap_callable_class<C>::type &type;
+};
+
+template<typename F, bool TestCallability = true> struct cpp0x_result_of_impl;
+
+#else // BOOST_NO_SFINAE_EXPR
+
+template<typename T>
+struct result_of_always_void
+{
+  typedef void type;
+};
+
+template<typename F, typename Enable = void> struct cpp0x_result_of_impl {};
+
+#endif // BOOST_NO_SFINAE_EXPR
 
 template<typename F>
 struct result_of_void_impl

test/result_of_test.cpp

@@ -5,7 +5,7 @@
 //  1.0. (See accompanying file LICENSE_1_0.txt or copy at
 //  http://www.boost.org/LICENSE_1_0.txt)
 
-#define BOOST_RESULT_OF_USE_DECLTYPE
+#include <boost/config.hpp>
 
 // For more information, see http://www.boost.org/libs/utility
 #include <boost/utility/result_of.hpp>
@@ -62,6 +62,9 @@ struct int_result_type_and_float_result_of_and_char_return_template
   char operator()(char);
 };
 
+template<typename T>
+struct cv_overload_check {};
+
 struct result_of_member_function_template
 {
   template<typename F> struct result;
@@ -69,13 +72,13 @@ struct result_of_member_function_template
   template<typename This, typename That> struct result<This(That)> { typedef That type; };
   template<class T> typename result<result_of_member_function_template(T)>::type operator()(T);
 
-  template<typename This, typename That> struct result<const This(That)> { typedef const That type; };
+  template<typename This, typename That> struct result<const This(That)> { typedef cv_overload_check<const That> type; };
   template<class T> typename result<const result_of_member_function_template(T)>::type operator()(T) const;
 
-  template<typename This, typename That> struct result<volatile This(That)> { typedef volatile That type; };
+  template<typename This, typename That> struct result<volatile This(That)> { typedef cv_overload_check<volatile That> type; };
   template<class T> typename result<volatile result_of_member_function_template(T)>::type operator()(T) volatile;
 
-  template<typename This, typename That> struct result<const volatile This(That)> { typedef const volatile That type; };
+  template<typename This, typename That> struct result<const volatile This(That)> { typedef cv_overload_check<const volatile That> type; };
   template<class T> typename result<const volatile result_of_member_function_template(T)>::type operator()(T) const volatile;
 
   template<typename This, typename That> struct result<This(That &, That)> { typedef That & type; };
@@ -91,13 +94,16 @@ struct result_of_member_function_template
   template<class T> typename result<result_of_member_function_template(T const volatile &, T)>::type operator()(T const volatile &, T);
 };
 
-struct no_result_type_or_result_of
+struct no_result_type_or_result
 {
-  int operator()(double);
-  short operator()(double) const;
-  unsigned int operator()();
-  unsigned short operator()() volatile;
-  const unsigned short operator()() const volatile;
+  short operator()(double);
+  cv_overload_check<const short> operator()(double) const;
+  cv_overload_check<volatile short> operator()(double) volatile;
+  cv_overload_check<const volatile short> operator()(double) const volatile;
+  int operator()();
+  cv_overload_check<const int> operator()() const;
+  cv_overload_check<volatile int> operator()() volatile;
+  cv_overload_check<const volatile int> operator()() const volatile;
 #if !defined(BOOST_NO_RVALUE_REFERENCES)
   short operator()(int&&);
   int operator()(int&);
@@ -106,13 +112,16 @@ struct no_result_type_or_result_of
 };
 
 template<typename T>
-struct no_result_type_or_result_of_template
+struct no_result_type_or_result_template
 {
-  int operator()(double);
-  short operator()(double) const;
-  unsigned int operator()();
-  unsigned short operator()() volatile;
-  const unsigned short operator()() const volatile;
+  short operator()(double);
+  cv_overload_check<const short> operator()(double) const;
+  cv_overload_check<volatile short> operator()(double) volatile;
+  cv_overload_check<const volatile short> operator()(double) const volatile;
+  int operator()();
+  cv_overload_check<const int> operator()() const;
+  cv_overload_check<volatile int> operator()() volatile;
+  cv_overload_check<const volatile int> operator()() const volatile;
 #if !defined(BOOST_NO_RVALUE_REFERENCES)
   short operator()(int&&);
   int operator()(int&);
@@ -120,6 +129,27 @@ struct no_result_type_or_result_of_template
 #endif
 };
 
+// sfinae_tests are derived from example code from Joel de Guzman,
+// which demonstrated the interaction between result_of and SFINAE.
+template <typename F, typename Arg>
+typename boost::result_of<F(Arg const&)>::type
+sfinae_test(F f, Arg const& arg)
+{
+    return f(arg);
+}
+
+template <typename F, typename Arg>
+typename boost::result_of<F(Arg&)>::type
+sfinae_test(F f, Arg& arg)
+{
+    return f(arg);
+}
+
+int sfinae_test_f(int& i)
+{
+    return i;
+}
+
 struct X {};
 
 int main()
@@ -130,6 +160,10 @@ int main()
   typedef int (&func_ref)(float, double);
   typedef int (*func_ptr_0)();
   typedef int (&func_ref_0)();
+  typedef void (*func_ptr_void)(float, double);
+  typedef void (&func_ref_void)(float, double);
+  typedef void (*func_ptr_void_0)();
+  typedef void (&func_ref_void_0)();
   typedef int (X::*mem_func_ptr)(float);
   typedef int (X::*mem_func_ptr_c)(float) const;
   typedef int (X::*mem_func_ptr_v)(float) volatile;
@@ -157,7 +191,7 @@ int main()
 
   // Prior to decltype, result_of could not deduce the return type
   // nullary function objects unless they exposed a result_type.
-#if !defined(BOOST_NO_DECLTYPE)
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE)
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_of(void)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<volatile int_result_of(void)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_of_template<void>(void)>::type, int>::value));
@@ -169,14 +203,11 @@ int main()
   BOOST_STATIC_ASSERT((is_same<result_of<volatile int_result_of_template<void>(void)>::type, void>::value));
 #endif
 
-  BOOST_STATIC_ASSERT((is_same<tr1_result_of<int_result_type_and_float_result_of_and_char_return(char)>::type, int>::value));
-  BOOST_STATIC_ASSERT((is_same<tr1_result_of<int_result_type_and_float_result_of_and_char_return_template<void>(char)>::type, int>::value));
-
   // Prior to decltype, result_of ignored a nested result<> if
   // result_type was defined. After decltype, result_of deduces the
   // actual return type of the function object, ignoring both
   // result<> and result_type.
-#if !defined(BOOST_NO_DECLTYPE)
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE)
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_type_and_float_result_of_and_char_return(char)>::type, char>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_type_and_float_result_of_and_char_return_template<void>(char)>::type, char>::value));
 #else
@@ -184,41 +215,52 @@ int main()
   BOOST_STATIC_ASSERT((is_same<result_of<int_result_type_and_float_result_of_and_char_return_template<void>(char)>::type, int>::value));
 #endif
 
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<int_result_type_and_float_result_of_and_char_return(char)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<int_result_type_and_float_result_of_and_char_return_template<void>(char)>::type, int>::value));
+
   BOOST_STATIC_ASSERT((is_same<result_of<func_ptr(char, float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<func_ref(char, float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<func_ptr_0()>::type, int>::value)); 
   BOOST_STATIC_ASSERT((is_same<result_of<func_ref_0()>::type, int>::value)); 
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ptr_void(char, float)>::type, void>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ref_void(char, float)>::type, void>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ptr_void_0()>::type, void>::value)); 
+  BOOST_STATIC_ASSERT((is_same<result_of<func_ref_void_0()>::type, void>::value)); 
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_c(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_v(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_cv(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<mem_func_ptr_0(X)>::type, int>::value)); 
-  BOOST_STATIC_ASSERT((is_same<result_of<func_ptr(void)>::type, int>::value));
 
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ptr(char, float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ref(char, float)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ptr_0()>::type, int>::value)); 
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ref_0()>::type, int>::value)); 
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ptr_void(char, float)>::type, void>::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ref_void(char, float)>::type, void>::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ptr_void_0()>::type, void>::value)); 
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ref_void_0()>::type, void>::value)); 
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<mem_func_ptr(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<mem_func_ptr_c(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<mem_func_ptr_v(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<mem_func_ptr_cv(X,char)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<mem_func_ptr_0(X)>::type, int>::value)); 
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ptr(void)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<func_ref(void)>::type, int>::value));
 
   BOOST_STATIC_ASSERT((is_same<result_of<result_of_member_function_template(double)>::type, double>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const result_of_member_function_template(double)>::type, const double>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<volatile result_of_member_function_template(double)>::type, volatile double>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const volatile result_of_member_function_template(double)>::type, const volatile double>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const result_of_member_function_template(double)>::type, cv_overload_check<const double> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<volatile result_of_member_function_template(double)>::type, cv_overload_check<volatile double> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const volatile result_of_member_function_template(double)>::type, cv_overload_check<const volatile double> >::value));
   BOOST_STATIC_ASSERT((is_same<result_of<result_of_member_function_template(int &, int)>::type, int &>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<result_of_member_function_template(int const &, int)>::type, int const &>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<result_of_member_function_template(int volatile &, int)>::type, int volatile &>::value));
   BOOST_STATIC_ASSERT((is_same<result_of<result_of_member_function_template(int const volatile &, int)>::type, int const volatile &>::value));
 
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<result_of_member_function_template(double)>::type, double>::value));
-  BOOST_STATIC_ASSERT((is_same<tr1_result_of<const result_of_member_function_template(double)>::type, const double>::value));
-  BOOST_STATIC_ASSERT((is_same<tr1_result_of<volatile result_of_member_function_template(double)>::type, volatile double>::value));
-  BOOST_STATIC_ASSERT((is_same<tr1_result_of<const volatile result_of_member_function_template(double)>::type, const volatile double>::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<const result_of_member_function_template(double)>::type, cv_overload_check<const double> >::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<volatile result_of_member_function_template(double)>::type, cv_overload_check<volatile double> >::value));
+  BOOST_STATIC_ASSERT((is_same<tr1_result_of<const volatile result_of_member_function_template(double)>::type, cv_overload_check<const volatile double> >::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<result_of_member_function_template(int &, int)>::type, int &>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<result_of_member_function_template(int const &, int)>::type, int const &>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<result_of_member_function_template(int volatile &, int)>::type, int volatile &>::value));
@@ -231,26 +273,38 @@ int main()
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<pf_t(int)>::type, int>::value));
   BOOST_STATIC_ASSERT((is_same<tr1_result_of<pf_t const(int)>::type,int>::value));
 
-#if !defined(BOOST_NO_DECLTYPE)
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(double)>::type, int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(void)>::type, unsigned int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result_of(double)>::type, short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result_of(void)>::type, unsigned short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result_of(void)>::type, const unsigned short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(double)>::type, int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(void)>::type, unsigned int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result_of_template<void>(double)>::type, short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result_of_template<void>(void)>::type, unsigned short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result_of_template<void>(void)>::type, const unsigned short>::value));
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE)
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result(double)>::type, short>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result(double)>::type, cv_overload_check<const short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result(double)>::type, cv_overload_check<volatile short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result(double)>::type, cv_overload_check<const volatile short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result(void)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result(void)>::type, cv_overload_check<const int> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result(void)>::type, cv_overload_check<volatile int> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result(void)>::type, cv_overload_check<const volatile int> >::value));
+
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_template<void>(double)>::type, short>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result_template<void>(double)>::type, cv_overload_check<const short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result_template<void>(double)>::type, cv_overload_check<volatile short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result_template<void>(double)>::type, cv_overload_check<const volatile short> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_template<void>(void)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const no_result_type_or_result_template<void>(void)>::type, cv_overload_check<const int> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<volatile no_result_type_or_result_template<void>(void)>::type, cv_overload_check<volatile int> >::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<const volatile no_result_type_or_result_template<void>(void)>::type, cv_overload_check<const volatile int> >::value));
 #if !defined(BOOST_NO_RVALUE_REFERENCES)
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int&&)>::type, short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int&)>::type, int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of(int const&)>::type, long>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int&&)>::type, short>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int&)>::type, int>::value));
-  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_of_template<void>(int const&)>::type, long>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result(int&&)>::type, short>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result(int&)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result(int const&)>::type, long>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_template<void>(int&&)>::type, short>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_template<void>(int&)>::type, int>::value));
+  BOOST_STATIC_ASSERT((is_same<result_of<no_result_type_or_result_template<void>(int const&)>::type, long>::value));
 #endif
 #endif
 
+#if defined(BOOST_RESULT_OF_USE_DECLTYPE)
+  int i = 123;
+  sfinae_test(sfinae_test_f, i);
+#endif // defined(BOOST_RESULT_OF_USE_DECLTYPE)
+
   return 0;
 }

utility.htm

@@ -143,7 +143,7 @@ void f() {
                 <h2><a name="result_of">Class template
                 result_of</a></h2> <p>The class template
                 <code>result_of</code> helps determine the type of a
-                call expression. Given an lvalue <code>f</code> of
+                call expression. For example, given an lvalue <code>f</code> of
                 type <code>F</code> and lvalues <code>t1</code>,
                 <code>t2</code>, ..., <code>t<em>N</em></code> of
                 types <code>T1</code>, <code>T2</code>, ...,
@@ -155,22 +155,24 @@ void f() {
                 the type <code>F</code> to be a function pointer,
                 function reference, member function pointer, or class
                 type. By default, <em>N</em> may be any value between 0 and
-                10. To change the upper limit, define the macro
+                16. To change the upper limit, define the macro
                 <code>BOOST_RESULT_OF_NUM_ARGS</code> to the maximum
                 value for <em>N</em>. Class template <code>result_of</code>
                 resides in the header <code>&lt;<a
                 href="../../boost/utility/result_of.hpp">boost/utility/result_of.hpp</a>&gt;</code>.</p>
 
-                <p>If your compiler supports <code>decltype</code>,
-                then you can enable automatic result type deduction by
-                defining the macro <code>BOOST_RESULT_OF_USE_DECLTYPE</code>,
-                as in the following example.</p>
+                <p>If your compiler's support for <code>decltype</code> is
+                adequate, <code>result_of</code> automatically uses it to
+                deduce the type of the call expression, in which case
+                <code>result_of&lt;F(T1, T2, ...,
+                T<em>N</em>)&gt;::type</code> names the type
+                <code>decltype(boost::declval&lt;F&gt;()(boost::declval&lt;T1&gt;(),
+                boost::declval&lt;T2&gt;(), ...,
+                boost::declval&lt;T<em>N</em>&gt;()))</code>, as in the
+                following example.</p>
 
                 <blockquote>
-                <pre>#define BOOST_RESULT_OF_USE_DECLTYPE
-#include &lt;boost/utility/result_of.hpp&gt;
-
-struct functor {
+                <pre>struct functor {
     template&lt;class T&gt;
     T operator()(T x)
     {
@@ -180,21 +182,29 @@ struct functor {
 
 typedef boost::result_of&lt;
     functor(int)
-&gt;::type type;</pre>
+&gt;::type type; // type is int</pre>
                 </blockquote>
 
-                <p>If <code>decltype</code> is not enabled,
+                <p>You can test whether <code>result_of</code> is using
+                <code>decltype</code> by checking if the macro
+                <code>BOOST_RESULT_OF_USE_DECLTYPE</code> is defined after
+                including <code>result_of.hpp</code>. You can also force
+                <code>result_of</code> to use <code>decltype</code> by
+                defining <code>BOOST_RESULT_OF_USE_DECLTYPE</code> prior
+                to including <code>result_of.hpp</code>.</p>
+
+                <p>If <code>decltype</code> is not used,
                 then automatic result type deduction of function
                 objects is not possible. Instead, <code>result_of</code>
                 uses the following protocol to allow the programmer to
                 specify a type. When <code>F</code> is a class type with a
                 member type <code>result_type</code>,
                 <code>result_of&lt;F(T1, T2, ...,
-                T<em>N</em>)&gt;</code> is
+                T<em>N</em>)&gt;::type</code> is
                 <code>F::result_type</code>. When <code>F</code> does
                 not contain <code>result_type</code>,
                 <code>result_of&lt;F(T1, T2, ...,
-                T<em>N</em>)&gt;</code> is <code>F::result&lt;F(T1,
+                T<em>N</em>)&gt;::type</code> is <code>F::result&lt;F(T1,
                 T2, ..., T<em>N</em>)&gt;::type</code> when
                 <code><em>N</em> &gt; 0</code> or <code>void</code>
                 when <code><em>N</em> = 0</code>. Note that it is the
@@ -221,22 +231,29 @@ typedef boost::result_of&lt;
 
 typedef boost::result_of&lt;
     functor(int)
-&gt;::type type;</pre>
+&gt;::type type; // type is int</pre>
                 </blockquote>
 
-                <p>In a future
-                release, <code>BOOST_RESULT_OF_USE_DECLTYPE</code>
-                may be enabled by default on compilers that
-                support <code>decltype</code>, so if you use the above
-                protocol please take care to ensure that
-                the <code>result_type</code>
-                and <code>result&lt;&gt;</code> members accurately
-                represent the result type. If you wish to continue to
+                <p>Since <code>decltype</code> is a new language
+                feature recently standardized in C++11,
+                if you are writing a function object
+                to be used with <code>result_of</code>, for
+                maximum portability, you might consider following
+                the above protocol even if your compiler has
+                proper <code>decltype</code> support. If you wish to continue to
                 use the protocol on compilers that
-                support <code>decltype</code>,
-                use <code>boost::tr1_result_of</code>, which is also
-                defined
-                in <code>&lt;<a href="../../boost/utility/result_of.hpp">boost/utility/result_of.hpp</a>&gt;</code>.</p>
+                support <code>decltype</code>, there are two options:
+                You can use <code>boost::tr1_result_of</code>, which is also
+                defined in <code>&lt;<a href="../../boost/utility/result_of.hpp">boost/utility/result_of.hpp</a>&gt;</code>.
+                Alternatively, you can define the macro
+                <code>BOOST_RESULT_OF_USE_TR1</code>, which causes
+                <code>result_of</code> to use the protocol described
+                above instead of <code>decltype</code>. If you choose to
+                follow the protocol, take care to ensure that the
+                <code>result_type</code> and
+                <code>result&lt;&gt;</code> members accurately
+                represent the return type of
+                <code>operator()</code> given a call expression.</p>
 
                 <a name="BOOST_NO_RESULT_OF"></a>
                 <p>This implementation of <code>result_of</code>
@@ -253,7 +270,322 @@ typedef boost::result_of&lt;
                 <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf">N1836</a>,
                 or, for motivation and design rationale,
                 the <code>result_of</code> <a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1454.html">proposal</a>.</p>
-                Contributed by Doug Gregor.</p>
+
+                <a name="result_of_guidelines">
+                <h3>Usage guidelines for boost::result_of</h3>
+                </a>
+
+                <p>The following are general suggestions about when
+                and how to use <code>boost::result_of</code>.</p>
+
+                <ol>
+                <li> If you are targeting C++11 and are not concerned
+                about portability to non-compliant compilers or
+                previous versions of the standard, then use
+                <code>std::result_of</code>. If <code>std::result_of</code>
+                meets your needs, then there's no reason to stop using
+                it.</li>
+
+                <li> If you are targeting C++11 but may port your code
+                to legacy compilers at some time in the future, then
+                use <code>boost::result_of</code> with
+                <code>decltype</code>. When <code>decltype</code> is
+                used <code>boost::result_of</code>
+                and <code>std::result_of</code> are usually
+                interchangeable. See the documentation on
+                known <a href="#result_of_cxx11_diff">differences</a>
+                between boost::result_of and C++11 result_of.</li>
+
+                <li> If compiler portability is required,
+                use <code>boost::result_of</code> with the TR1 protocol.</li>
+                </ol>
+
+                <p>Regardless of how you
+                configure <code>boost::result_of</code>, it is
+                important to bear in mind that the return type of a
+                function may change depending on its arguments, and
+                additionally, the return type of a member function may
+                change depending on the cv-qualification of the
+                object. <code>boost::result_of</code> must be passed
+                the appropriately cv-qualified types in order to
+                deduce the corresponding return type. For example:
+
+                <blockquote>
+                <pre>struct functor {
+    int& operator()(int);
+    int const& operator()(int) const;
+
+    float& operator()(float&);
+    float const& operator()(float const&);
+};
+
+typedef boost::result_of&lt;
+    functor(int)
+&gt;::type type1; // type1 is int &
+
+typedef boost::result_of&lt;
+    const functor(int)
+&gt;::type type2; // type2 is int const &
+
+typedef boost::result_of&lt;
+    functor(float&)
+&gt;::type type3; // type3 is float &
+
+typedef boost::result_of&lt;
+    functor(float const&)
+&gt;::type type4; // type4 is float const &</pre>
+                </blockquote>
+
+                <a name="result_of_tr1_protocol_guidelines">
+                <h3>Usage guidelines for the TR1 result_of protocol</h3>
+                </a>
+
+                <p>On compliant C++11
+                compilers, <code>boost::result_of</code> can
+                use <code>decltype</code> to deduce the type of any
+                call expression, including calls to function
+                objects. However, on pre-C++11 compilers or on
+                compilers without adequate decltype support,
+                additional scaffolding is needed from function
+                objects as described above. The following are
+                suggestions about how to use the TR1 protocol.</p>
+
+                <ul>
+                    <li>When the return type does not depend on the
+                    argument types or the cv-qualification of the
+                    function object, simply
+                    define <code>result_type</code>. There is no need
+                    to use the <code>result</code> template unless the
+                    return type varies.</li>
+
+                    <li>Use the protocol specified type when defining
+                    function prototypes. This can help ensure the
+                    actual return type does not get out of sync with
+                    the protocol specification. For example:
+
+                   <blockquote>
+                   <pre>struct functor {
+    typedef int result_type;
+    result_type operator()(int);
+};</pre>
+                   </blockquote> </li>
+
+                   <li>Always specify the <code>result</code>
+                   specialization near the corresponding
+                   <code>operator()</code> overload. This can make it
+                   easier to keep the specializations in sync with the
+                   overloads. For example:
+
+                   <blockquote>
+                   <pre>struct functor {
+    template&lt;class&gt; struct result;
+
+    template&lt;class F&gt;
+    struct result&lt;F(int)&gt; {
+        typedef int& type;
+    };
+    result&lt;functor(int)&gt;::type operator()(int);
+
+    template&lt;class F&gt;
+    struct result&lt;const F(int)&gt; {
+        typedef int const& type;
+    };
+    result&lt;const functor(int)&gt;::type operator()(int) const;
+};</pre>
+                   </blockquote> </li>
+
+                   <li>Use type transformations to simplify
+                   the <code>result</code> template specialization. For
+                   example, the following uses
+                   <a href="../type_traits/doc/html/index.html">Boost.TypeTraits</a>
+                   to specialize the <code>result</code> template for
+                   a single <code>operator()</code> that can be called on
+                   both a const and non-const function object with
+                   either an lvalue or rvalue argument.
+
+                   <blockquote>
+                   <pre>struct functor {
+    template&lt;class&gt; struct result;
+
+    template&lt;class F, class T&gt;
+    struct result&lt;F(T)&gt; 
+        : boost::remove_cv&lt;
+              typename boost::remove_reference&lt;T&gt;::type
+          &gt;
+    {};
+
+    template&lt;class T&gt;
+    T operator()(T const&amp; x) const;
+};</pre>
+                   </blockquote></li>
+                </ul>
+
+                <a name="result_of_tr1_diff">
+                <h3>Known differences between boost::result_of and TR1 result_of</h3>
+                </a>
+
+                When using <code>decltype</code>, <code>boost::result_of</code>
+                ignores the TR1 protocol and instead deduces the
+                return type of function objects directly
+                via <code>decltype</code>. In most situations, users
+                will not notice a difference, so long as they use the
+                protocol correctly. The following are situations in
+                which the type deduced
+                by <code>boost::result_of</code> is known to differ depending on
+                whether <code>decltype</code> or the TR1 protocol is
+                used.
+
+                <ul>
+                <li> TR1 protocol misusage
+
+                     <p>When using the TR1
+                     protocol, <code>boost::result_of</code> cannot
+                     detect whether the actual type of a call to a
+                     function object is the same as the type specified
+                     by the protocol, which allows for the possibility
+                     of inadvertent mismatches between the specified
+                     type and the actual type. When
+                     using <code>decltype</code>, these subtle bugs
+                     may result in compilation errors. For example:</p>
+
+                     <blockquote>
+                     <pre>struct functor {
+   typedef short result_type;
+   int operator()(short);
+};
+
+#ifdef BOOST_RESULT_OF_USE_DECLTYPE
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;boost::result_of&lt;functor(short)&gt;::type, int&gt;::value
+)); 
+
+#else
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;boost::result_of&lt;functor(short)&gt;::type, short&gt;::value
+));
+
+#endif</pre>
+                   </blockquote>
+
+                  <p>Note that the user can
+                  force <code>boost::result_of</code> to use the TR1
+                  protocol even on platforms that
+                  support <code>decltype</code> by
+                  defining <code>BOOST_RESULT_OF_USE_TR1</code>.</p></li>
+
+                  <li> Nullary function objects
+
+                       <p>When using the TR1 protocol, <code>boost::result_of</code>
+                       cannot always deduce the type of calls to
+                       nullary function objects, in which case the
+                       type defaults to void. When using <code>decltype</code>,
+                       <code>boost::result_of</code> always gives the actual type of the
+                       call expression. For example:</p>
+
+                       <blockquote>
+                       <pre>struct functor {
+   template&lt;class&gt; struct result {
+       typedef int type;
+   };
+   int operator()();
+};
+
+#ifdef BOOST_RESULT_OF_USE_DECLTYPE
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;boost::result_of&lt;functor()&gt;::type, int&gt;::value
+));
+
+#else
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;boost::result_of&lt;functor()&gt;::type, void&gt;::value
+));
+
+#endif</pre>
+                       </blockquote>
+
+                       <p>Note that there are some workarounds for the
+                       nullary function problem. So long as the return
+                       type does not vary,
+                       <code>result_type</code> can always be used to
+                       specify the return type regardless of arity. If the
+                       return type does vary, then the user can
+                       specialize <code>boost::result_of</code> itself for
+                       nullary calls.</p></li>
+
+                  <li> Non-class prvalues and cv-qualification
+
+                       <p>When using the TR1
+                       protocol, <code>boost::result_of</code> will
+                       report the cv-qualified type specified
+                       by <code>result_type</code> or
+                       the <code>result</code> template regardless of
+                       the actual cv-qualification of the call
+                       expression. When using
+                       <code>decltype</code>, <code>boost::result_of</code>
+                       will report the actual type of the call expression,
+                       which is not cv-qualified when the expression is a
+                       non-class prvalue. For example:</p>
+
+                       <blockquote>
+                       <pre>struct functor {
+   template&lt;class&gt; struct result;
+   template&lt;class F, class T&gt; struct result&lt;F(const T)&gt; {
+       typedef const T type;
+   };
+
+   const short operator()(const short);
+   int const & operator()(int const &);
+};
+
+// Non-prvalue call expressions work the same with or without decltype.
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;
+       boost::result_of&lt;functor(int const &)&gt;::type,
+       int const &
+::value
+));
+
+// Non-class prvalue call expressions are not actually cv-qualified,
+// but only the decltype-based result_of reports this accurately.
+
+#ifdef BOOST_RESULT_OF_USE_DECLTYPE
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;
+       boost::result_of&lt;functor(const short)&gt;::type,
+       short
+::value
+));
+
+#else
+
+BOOST_STATIC_ASSERT((
+   boost::is_same&lt;
+       boost::result_of&lt;functor(const short)&gt;::type,
+       const short
+::value
+));
+
+#endif</pre>
+                       </blockquote></li>
+                </ul>
+
+                <a name="result_of_cxx11_diff">
+                <h3>Known differences between boost::result_of and C++11 result_of</h3>
+                </a>
+
+                <p>When using <code>decltype</code>, <code>boost::result_of</code>
+                implements most of the C++11 result_of
+                specification. One known exception is that
+                <code>boost::result_of</code> does not implement the
+                requirements regarding pointers to member data.</p>
+
+                <p>Created by Doug Gregor. Contributions from Daniel Walker, Eric Niebler, Michel Morin and others</p>
 
 		<h2>Class templates for the Base-from-Member Idiom</h2>
 		<p>See <a href="base_from_member.html">separate documentation</a>.</p>