boost_function/include/boost/function/function_template.hpp

// Boost.Function library

//  Copyright Douglas Gregor 2001-2006
//  Copyright Emil Dotchevski 2007
//  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

// Note: this header is a header template and must NOT have multiple-inclusion
// protection.
#include <boost/function/detail/prologue.hpp>

#if defined(BOOST_MSVC)
#   pragma warning( push )
#   pragma warning( disable : 4127 ) // "conditional expression is constant"
#endif       

#define BOOST_FUNCTION_TEMPLATE_PARMS BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS, typename T)

#define BOOST_FUNCTION_TEMPLATE_ARGS BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS, T)

#define BOOST_FUNCTION_PARM(J,I,D) BOOST_PP_CAT(T,I) BOOST_PP_CAT(a,I)

#define BOOST_FUNCTION_PARMS BOOST_PP_ENUM(BOOST_FUNCTION_NUM_ARGS,BOOST_FUNCTION_PARM,BOOST_PP_EMPTY)

#define BOOST_FUNCTION_ARGS BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS, a)

#define BOOST_FUNCTION_ARG_TYPE(J,I,D) \
  typedef BOOST_PP_CAT(T,I) BOOST_PP_CAT(BOOST_PP_CAT(arg, BOOST_PP_INC(I)),_type);

#define BOOST_FUNCTION_ARG_TYPES BOOST_PP_REPEAT(BOOST_FUNCTION_NUM_ARGS,BOOST_FUNCTION_ARG_TYPE,BOOST_PP_EMPTY)

// Comma if nonzero number of arguments
#if BOOST_FUNCTION_NUM_ARGS == 0
#  define BOOST_FUNCTION_COMMA
#else
#  define BOOST_FUNCTION_COMMA ,
#endif // BOOST_FUNCTION_NUM_ARGS > 0

// Class names used in this version of the code
#define BOOST_FUNCTION_FUNCTION BOOST_JOIN(function,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_FUNCTION_INVOKER \
  BOOST_JOIN(function_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_VOID_FUNCTION_INVOKER \
  BOOST_JOIN(void_function_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_FUNCTION_OBJ_INVOKER \
  BOOST_JOIN(function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER \
  BOOST_JOIN(void_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_FUNCTION_REF_INVOKER \
  BOOST_JOIN(function_ref_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_VOID_FUNCTION_REF_INVOKER \
  BOOST_JOIN(void_function_ref_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_GET_FUNCTION_INVOKER \
  BOOST_JOIN(get_function_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER \
  BOOST_JOIN(get_function_obj_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_GET_FUNCTION_REF_INVOKER \
  BOOST_JOIN(get_function_ref_invoker,BOOST_FUNCTION_NUM_ARGS)
#define BOOST_FUNCTION_VTABLE BOOST_JOIN(basic_vtable,BOOST_FUNCTION_NUM_ARGS)

#ifndef BOOST_NO_VOID_RETURNS
#  define BOOST_FUNCTION_VOID_RETURN_TYPE void
#  define BOOST_FUNCTION_RETURN(X) X
#else
#  define BOOST_FUNCTION_VOID_RETURN_TYPE boost::detail::function::unusable
#  define BOOST_FUNCTION_RETURN(X) X; return BOOST_FUNCTION_VOID_RETURN_TYPE ()
#endif

namespace boost {
  namespace detail {
    namespace function {
      template<
        typename FunctionPtr,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
        >
      struct BOOST_FUNCTION_FUNCTION_INVOKER
      {
        static R invoke(function_buffer& function_ptr BOOST_FUNCTION_COMMA
                        BOOST_FUNCTION_PARMS)
        {
          FunctionPtr f = reinterpret_cast<FunctionPtr>(function_ptr.func_ptr);
          return f(BOOST_FUNCTION_ARGS);
        }
      };

      template<
        typename FunctionPtr,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
        >
      struct BOOST_FUNCTION_VOID_FUNCTION_INVOKER
      {
        static BOOST_FUNCTION_VOID_RETURN_TYPE
        invoke(function_buffer& function_ptr BOOST_FUNCTION_COMMA
               BOOST_FUNCTION_PARMS)

        {
          FunctionPtr f = reinterpret_cast<FunctionPtr>(function_ptr.func_ptr);
          BOOST_FUNCTION_RETURN(f(BOOST_FUNCTION_ARGS));
        }
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
      >
      struct BOOST_FUNCTION_FUNCTION_OBJ_INVOKER
      {
        static R invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA
                        BOOST_FUNCTION_PARMS)

        {
          FunctionObj* f;
          if (function_allows_small_object_optimization<FunctionObj>::value)
            f = reinterpret_cast<FunctionObj*>(&function_obj_ptr.data);
          else
            f = reinterpret_cast<FunctionObj*>(function_obj_ptr.obj_ptr);
          return (*f)(BOOST_FUNCTION_ARGS);
        }
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
      >
      struct BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER
      {
        static BOOST_FUNCTION_VOID_RETURN_TYPE
        invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA
               BOOST_FUNCTION_PARMS)

        {
          FunctionObj* f;
          if (function_allows_small_object_optimization<FunctionObj>::value)
            f = reinterpret_cast<FunctionObj*>(&function_obj_ptr.data);
          else
            f = reinterpret_cast<FunctionObj*>(function_obj_ptr.obj_ptr);
          BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));
        }
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
      >
      struct BOOST_FUNCTION_FUNCTION_REF_INVOKER
      {
        static R invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA
                        BOOST_FUNCTION_PARMS)

        {
          FunctionObj* f = 
            reinterpret_cast<FunctionObj*>(function_obj_ptr.obj_ptr);
          return (*f)(BOOST_FUNCTION_ARGS);
        }
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
      >
      struct BOOST_FUNCTION_VOID_FUNCTION_REF_INVOKER
      {
        static BOOST_FUNCTION_VOID_RETURN_TYPE
        invoke(function_buffer& function_obj_ptr BOOST_FUNCTION_COMMA
               BOOST_FUNCTION_PARMS)

        {
          FunctionObj* f = 
            reinterpret_cast<FunctionObj*>(function_obj_ptr.obj_ptr);
          BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));
        }
      };

      template<
        typename FunctionPtr,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
      >
      struct BOOST_FUNCTION_GET_FUNCTION_INVOKER
      {
        typedef typename mpl::if_c<(is_void<R>::value),
                            BOOST_FUNCTION_VOID_FUNCTION_INVOKER<
                            FunctionPtr,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >,
                          BOOST_FUNCTION_FUNCTION_INVOKER<
                            FunctionPtr,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >
                       >::type type;
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
       >
      struct BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER
      {
        typedef typename mpl::if_c<(is_void<R>::value),
                            BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER<
                            FunctionObj,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >,
                          BOOST_FUNCTION_FUNCTION_OBJ_INVOKER<
                            FunctionObj,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >
                       >::type type;
      };

      template<
        typename FunctionObj,
        typename R BOOST_FUNCTION_COMMA
        BOOST_FUNCTION_TEMPLATE_PARMS
       >
      struct BOOST_FUNCTION_GET_FUNCTION_REF_INVOKER
      {
        typedef typename mpl::if_c<(is_void<R>::value),
                            BOOST_FUNCTION_VOID_FUNCTION_REF_INVOKER<
                            FunctionObj,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >,
                          BOOST_FUNCTION_FUNCTION_REF_INVOKER<
                            FunctionObj,
                            R BOOST_FUNCTION_COMMA
                            BOOST_FUNCTION_TEMPLATE_ARGS
                          >
                       >::type type;
      };

      /**
       * vtable for a specific boost::function instance.
       */
      template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
      struct BOOST_FUNCTION_VTABLE : vtable_base
      {
#ifndef BOOST_NO_VOID_RETURNS
        typedef R         result_type;
#else
        typedef typename function_return_type<R>::type result_type;
#endif // BOOST_NO_VOID_RETURNS

        typedef result_type (*invoker_type)(function_buffer&
                                            BOOST_FUNCTION_COMMA
                                            BOOST_FUNCTION_TEMPLATE_ARGS);

        template<typename F>
        BOOST_FUNCTION_VTABLE(F f) : vtable_base(), invoker(0)
        {
          init(f);
        }
        template<typename F,typename Allocator>
        BOOST_FUNCTION_VTABLE(F f, Allocator) : vtable_base(), invoker(0)
        {
          init_a<Allocator>(f);
        }

        template<typename F>
        bool assign_to(F f, function_buffer& functor)
        {
          typedef typename get_function_tag<F>::type tag;
          return assign_to(f, functor, tag());
        }
        template<typename F,typename Allocator>
        bool assign_to_a(F f, function_buffer& functor, Allocator a)
        {
          typedef typename get_function_tag<F>::type tag;
          return assign_to_a(f, functor, a, tag());
        }

        void clear(function_buffer& functor)
        {
          if (manager)
            manager(functor, functor, destroy_functor_tag);
        }

      private:
        template<typename F>
        void init(F f)
        {
          typedef typename get_function_tag<F>::type tag;
          init(f, tag());
        }
        template<typename Allocator,typename F>
        void init_a(F f)
        {
          typedef typename get_function_tag<F>::type tag;
          init_a<Allocator>(f, tag());
        }

        // Function pointers
        template<typename FunctionPtr>
        void init(FunctionPtr /*f*/, function_ptr_tag)
        {
          typedef typename BOOST_FUNCTION_GET_FUNCTION_INVOKER<
                             FunctionPtr,
                             R BOOST_FUNCTION_COMMA
                             BOOST_FUNCTION_TEMPLATE_ARGS
                           >::type
            actual_invoker_type;

          invoker = &actual_invoker_type::invoke;
          manager = &functor_manager<FunctionPtr>::manage;
        }
        template<typename Allocator,typename FunctionPtr>
        void init_a(FunctionPtr f, function_ptr_tag)
        {
          typedef typename BOOST_FUNCTION_GET_FUNCTION_INVOKER<
                             FunctionPtr,
                             R BOOST_FUNCTION_COMMA
                             BOOST_FUNCTION_TEMPLATE_ARGS
                           >::type
            actual_invoker_type;

          invoker = &actual_invoker_type::invoke;
          manager = &functor_manager_a<FunctionPtr, Allocator>::manage;
        }

        template<typename FunctionPtr>
        bool 
        assign_to(FunctionPtr f, function_buffer& functor, function_ptr_tag)
        {
          this->clear(functor);
          if (f) {
            // should be a reinterpret cast, but some compilers insist
            // on giving cv-qualifiers to free functions
            functor.func_ptr = (void (*)())(f);
            return true;
          } else {
            return false;
          }
        }
        template<typename FunctionPtr,typename Allocator>
        bool 
        assign_to_a(FunctionPtr f, function_buffer& functor, Allocator, function_ptr_tag)
        {
          return assign_to(f,functor,function_ptr_tag());
        }

        // Member pointers
#if BOOST_FUNCTION_NUM_ARGS > 0
        template<typename MemberPtr>
        void init(MemberPtr f, member_ptr_tag)
        {
          // DPG TBD: Add explicit support for member function
          // objects, so we invoke through mem_fn() but we retain the
          // right target_type() values.
          this->init(mem_fn(f));
        }
        template<typename Allocator,typename MemberPtr>
        void init_a(MemberPtr f, member_ptr_tag)
        {
          // DPG TBD: Add explicit support for member function
          // objects, so we invoke through mem_fn() but we retain the
          // right target_type() values.
          this->init_a<Allocator>(mem_fn(f));
        }

        template<typename MemberPtr>
        bool assign_to(MemberPtr f, function_buffer& functor, member_ptr_tag)
        {
          // DPG TBD: Add explicit support for member function
          // objects, so we invoke through mem_fn() but we retain the
          // right target_type() values.
          if (f) {
            this->assign_to(mem_fn(f), functor);
            return true;
          } else {
            return false;
          }
        }
        template<typename MemberPtr,typename Allocator>
        bool assign_to_a(MemberPtr f, function_buffer& functor, Allocator a, member_ptr_tag)
        {
          // DPG TBD: Add explicit support for member function
          // objects, so we invoke through mem_fn() but we retain the
          // right target_type() values.
          if (f) {
            this->assign_to_a(mem_fn(f), functor, a);
            return true;
          } else {
            return false;
          }
        }
#endif // BOOST_FUNCTION_NUM_ARGS > 0

        // Function objects
        template<typename FunctionObj>
        void init(FunctionObj /*f*/, function_obj_tag)
        {
          typedef typename BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER<
                             FunctionObj,
                             R BOOST_FUNCTION_COMMA
                             BOOST_FUNCTION_TEMPLATE_ARGS
                           >::type
            actual_invoker_type;

          invoker = &actual_invoker_type::invoke;
          manager = &functor_manager<FunctionObj>::manage;
        }
        template<typename Allocator,typename FunctionObj>
        void init_a(FunctionObj /*f*/, function_obj_tag)
        {
          typedef typename BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER<
                             FunctionObj,
                             R BOOST_FUNCTION_COMMA
                             BOOST_FUNCTION_TEMPLATE_ARGS
                           >::type
            actual_invoker_type;

          invoker = &actual_invoker_type::invoke;
          manager = &functor_manager_a<FunctionObj, Allocator>::manage;
        }

        // Assign to a function object using the small object optimization
        template<typename FunctionObj>
        void 
        assign_functor(FunctionObj f, function_buffer& functor, mpl::true_)
        {
          new ((void*)&functor.data) FunctionObj(f);
        }
        template<typename FunctionObj,typename Allocator>
        void 
        assign_functor_a(FunctionObj f, function_buffer& functor, Allocator, mpl::true_)
        {
          assign_functor(f,functor,mpl::true_());
        }

        // Assign to a function object allocated on the heap.
        template<typename FunctionObj>
        void 
        assign_functor(FunctionObj f, function_buffer& functor, mpl::false_)
        {
          functor.obj_ptr = new FunctionObj(f);
        }
        template<typename FunctionObj,typename Allocator>
        void 
        assign_functor_a(FunctionObj f, function_buffer& functor, Allocator a, mpl::false_)
        {
          typedef functor_wrapper<FunctionObj,Allocator> functor_wrapper_type;
          typedef typename Allocator::template rebind<functor_wrapper_type>::other
            wrapper_allocator_type;
          typedef typename wrapper_allocator_type::pointer wrapper_allocator_pointer_type;
          wrapper_allocator_type wrapper_allocator(a);
          wrapper_allocator_pointer_type copy = wrapper_allocator.allocate(1);
          wrapper_allocator.construct(copy, functor_wrapper_type(f,a));
          functor_wrapper_type* new_f = static_cast<functor_wrapper_type*>(copy);
          functor.obj_ptr = new_f;
        }

        template<typename FunctionObj>
        bool 
        assign_to(FunctionObj f, function_buffer& functor, function_obj_tag)
        {
          if (!boost::detail::function::has_empty_target(boost::addressof(f))) {
            assign_functor(f, functor, 
                           mpl::bool_<(function_allows_small_object_optimization<FunctionObj>::value)>());
            return true;
          } else {
            return false;
          }
        }
        template<typename FunctionObj,typename Allocator>
        bool 
        assign_to_a(FunctionObj f, function_buffer& functor, Allocator a, function_obj_tag)
        {
          if (!boost::detail::function::has_empty_target(boost::addressof(f))) {
            assign_functor_a(f, functor, a,
                           mpl::bool_<(function_allows_small_object_optimization<FunctionObj>::value)>());
            return true;
          } else {
            return false;
          }
        }

        // Reference to a function object
        template<typename FunctionObj>
        void 
        init(const reference_wrapper<FunctionObj>& /*f*/, function_obj_ref_tag)
        {
          typedef typename BOOST_FUNCTION_GET_FUNCTION_REF_INVOKER<
                             FunctionObj,
                             R BOOST_FUNCTION_COMMA
                             BOOST_FUNCTION_TEMPLATE_ARGS
                           >::type
            actual_invoker_type;

          invoker = &actual_invoker_type::invoke;
          manager = &reference_manager<FunctionObj>::get;
        }
        template<typename Allocator,typename FunctionObj>
        void 
        init_a(const reference_wrapper<FunctionObj>& f, function_obj_ref_tag)
        {
          init(f,function_obj_ref_tag());
        }

        template<typename FunctionObj>
        bool 
        assign_to(const reference_wrapper<FunctionObj>& f, 
                  function_buffer& functor, function_obj_ref_tag)
        {
          if (!boost::detail::function::has_empty_target(f.get_pointer())) {
            // DPG TBD: We might need to detect constness of
            // FunctionObj to assign into obj_ptr or const_obj_ptr to
            // be truly legit, but no platform in existence makes
            // const void* different from void*.
            functor.const_obj_ptr = f.get_pointer();
            return true;
          } else {
            return false;
          }
        }
        template<typename FunctionObj,typename Allocator>
        bool 
        assign_to_a(const reference_wrapper<FunctionObj>& f, 
                  function_buffer& functor, Allocator, function_obj_ref_tag)
        {
          return assign_to(f,functor,function_obj_ref_tag());
        }

      public:
        invoker_type invoker;
      };
    } // end namespace function
  } // end namespace detail

  template<
    typename R BOOST_FUNCTION_COMMA
    BOOST_FUNCTION_TEMPLATE_PARMS
  >
  class BOOST_FUNCTION_FUNCTION : public function_base

#if BOOST_FUNCTION_NUM_ARGS == 1

    , public std::unary_function<T0,R>

#elif BOOST_FUNCTION_NUM_ARGS == 2

    , public std::binary_function<T0,T1,R>

#endif

  {
  public:
#ifndef BOOST_NO_VOID_RETURNS
    typedef R         result_type;
#else
    typedef  typename boost::detail::function::function_return_type<R>::type
      result_type;
#endif // BOOST_NO_VOID_RETURNS

  private:
    typedef boost::detail::function::BOOST_FUNCTION_VTABLE<
              R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
      vtable_type;

    struct clear_type {};

  public:
    BOOST_STATIC_CONSTANT(int, args = BOOST_FUNCTION_NUM_ARGS);

    // add signature for boost::lambda
    template<typename Args>
    struct sig
    {
      typedef result_type type;
    };

#if BOOST_FUNCTION_NUM_ARGS == 1
    typedef T0 argument_type;
#elif BOOST_FUNCTION_NUM_ARGS == 2
    typedef T0 first_argument_type;
    typedef T1 second_argument_type;
#endif

    BOOST_STATIC_CONSTANT(int, arity = BOOST_FUNCTION_NUM_ARGS);
    BOOST_FUNCTION_ARG_TYPES

    typedef BOOST_FUNCTION_FUNCTION self_type;

    BOOST_FUNCTION_FUNCTION() : function_base() { }

    // MSVC chokes if the following two constructors are collapsed into
    // one with a default parameter.
    template<typename Functor>
    BOOST_FUNCTION_FUNCTION(Functor BOOST_FUNCTION_TARGET_FIX(const &) f
#ifndef BOOST_NO_SFINAE
                            ,typename enable_if_c<
                            (boost::type_traits::ice_not<
                             (is_integral<Functor>::value)>::value),
                                        int>::type = 0
#endif // BOOST_NO_SFINAE
                            ) :
      function_base()
    {
      this->assign_to(f);
    }
    template<typename Functor,typename Allocator>
    BOOST_FUNCTION_FUNCTION(Functor BOOST_FUNCTION_TARGET_FIX(const &) f, Allocator a
#ifndef BOOST_NO_SFINAE
                            ,typename enable_if_c<
                            (boost::type_traits::ice_not<
                             (is_integral<Functor>::value)>::value),
                                        int>::type = 0
#endif // BOOST_NO_SFINAE
                            ) :
      function_base()
    {
      this->assign_to_a(f,a);
    }

#ifndef BOOST_NO_SFINAE
    BOOST_FUNCTION_FUNCTION(clear_type*) : function_base() { }
#else
    BOOST_FUNCTION_FUNCTION(int zero) : function_base()
    {
      BOOST_ASSERT(zero == 0);
    }
#endif

    BOOST_FUNCTION_FUNCTION(const BOOST_FUNCTION_FUNCTION& f) : function_base()
    {
      this->assign_to_own(f);
    }

    ~BOOST_FUNCTION_FUNCTION() { clear(); }

#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
    // MSVC 6.0 and prior require all definitions to be inline, but
    // these definitions can become very costly.
    result_type operator()(BOOST_FUNCTION_PARMS) const
    {
      if (this->empty())
        boost::throw_exception(bad_function_call());

      return static_cast<vtable_type*>(vtable)->invoker
               (this->functor BOOST_FUNCTION_COMMA BOOST_FUNCTION_ARGS);
    }
#else
    result_type operator()(BOOST_FUNCTION_PARMS) const;
#endif

    // The distinction between when to use BOOST_FUNCTION_FUNCTION and
    // when to use self_type is obnoxious. MSVC cannot handle self_type as
    // the return type of these assignment operators, but Borland C++ cannot
    // handle BOOST_FUNCTION_FUNCTION as the type of the temporary to
    // construct.
    template<typename Functor>
#ifndef BOOST_NO_SFINAE
    typename enable_if_c<
               (boost::type_traits::ice_not<
                 (is_integral<Functor>::value)>::value),
               BOOST_FUNCTION_FUNCTION&>::type
#else
    BOOST_FUNCTION_FUNCTION&
#endif
    operator=(Functor BOOST_FUNCTION_TARGET_FIX(const &) f)
    {
      this->clear();
      try {
        this->assign_to(f);
      } catch (...) {
        vtable = 0;
        throw;
      }
      return *this;
    }
    template<typename Functor,typename Allocator>
    void assign(Functor BOOST_FUNCTION_TARGET_FIX(const &) f, Allocator a)
    {
      this->clear();
      try {
        this->assign_to_a(f,a);
      } catch (...) {
        vtable = 0;
        throw;
      }
    }

#ifndef BOOST_NO_SFINAE
    BOOST_FUNCTION_FUNCTION& operator=(clear_type*)
    {
      this->clear();
      return *this;
    }
#else
    BOOST_FUNCTION_FUNCTION& operator=(int zero)
    {
      BOOST_ASSERT(zero == 0);
      this->clear();
      return *this;
    }
#endif

    // Assignment from another BOOST_FUNCTION_FUNCTION
    BOOST_FUNCTION_FUNCTION& operator=(const BOOST_FUNCTION_FUNCTION& f)
    {
      if (&f == this)
        return *this;

      this->clear();
      try {
        this->assign_to_own(f);
      } catch (...) {
        vtable = 0;
        throw;
      }
      return *this;
    }

    void swap(BOOST_FUNCTION_FUNCTION& other)
    {
      if (&other == this)
        return;

      BOOST_FUNCTION_FUNCTION tmp = *this;
      *this = other;
      other = tmp;
    }

    // Clear out a target, if there is one
    void clear()
    {
      if (vtable) {
        static_cast<vtable_type*>(vtable)->clear(this->functor);
        vtable = 0;
      }
    }

#if (defined __SUNPRO_CC) && (__SUNPRO_CC <= 0x530) && !(defined BOOST_NO_COMPILER_CONFIG)
    // Sun C++ 5.3 can't handle the safe_bool idiom, so don't use it
    operator bool () const { return !this->empty(); }
#else
  private:
    struct dummy {
      void nonnull() {};
    };

    typedef void (dummy::*safe_bool)();

  public:
    operator safe_bool () const
      { return (this->empty())? 0 : &dummy::nonnull; }

    bool operator!() const
      { return this->empty(); }
#endif

  private:
    void assign_to_own(const BOOST_FUNCTION_FUNCTION& f)
    {
      if (!f.empty()) {
        this->vtable = f.vtable;
        f.vtable->manager(f.functor, this->functor,
                          boost::detail::function::clone_functor_tag);
      }
    }

    template<typename Functor>
    void assign_to(Functor f)
    {
      static vtable_type stored_vtable(f);
      if (stored_vtable.assign_to(f, functor)) vtable = &stored_vtable;
      else vtable = 0;
    }
    template<typename Functor,typename Allocator>
    void assign_to_a(Functor f,Allocator a)
    {
      static vtable_type stored_vtable(f,a);
      if (stored_vtable.assign_to_a(f, functor, a)) vtable = &stored_vtable;
      else vtable = 0;
    }
  };

  template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
  inline void swap(BOOST_FUNCTION_FUNCTION<
                     R BOOST_FUNCTION_COMMA
                     BOOST_FUNCTION_TEMPLATE_ARGS
                   >& f1,
                   BOOST_FUNCTION_FUNCTION<
                     R BOOST_FUNCTION_COMMA
                     BOOST_FUNCTION_TEMPLATE_ARGS
                   >& f2)
  {
    f1.swap(f2);
  }

#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
  template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
  typename BOOST_FUNCTION_FUNCTION<
      R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>::result_type
   BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
  ::operator()(BOOST_FUNCTION_PARMS) const
  {
    if (this->empty())
      boost::throw_exception(bad_function_call());

    return static_cast<vtable_type*>(vtable)->invoker
             (this->functor BOOST_FUNCTION_COMMA BOOST_FUNCTION_ARGS);
  }
#endif

// Poison comparisons between boost::function objects of the same type.
template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
  void operator==(const BOOST_FUNCTION_FUNCTION<
                          R BOOST_FUNCTION_COMMA
                          BOOST_FUNCTION_TEMPLATE_ARGS>&,
                  const BOOST_FUNCTION_FUNCTION<
                          R BOOST_FUNCTION_COMMA
                          BOOST_FUNCTION_TEMPLATE_ARGS>&);
template<typename R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_PARMS>
  void operator!=(const BOOST_FUNCTION_FUNCTION<
                          R BOOST_FUNCTION_COMMA
                          BOOST_FUNCTION_TEMPLATE_ARGS>&,
                  const BOOST_FUNCTION_FUNCTION<
                          R BOOST_FUNCTION_COMMA
                          BOOST_FUNCTION_TEMPLATE_ARGS>& );

#if !defined(BOOST_FUNCTION_NO_FUNCTION_TYPE_SYNTAX)

#if BOOST_FUNCTION_NUM_ARGS == 0
#define BOOST_FUNCTION_PARTIAL_SPEC R (void)
#else
#define BOOST_FUNCTION_PARTIAL_SPEC R (BOOST_PP_ENUM_PARAMS(BOOST_FUNCTION_NUM_ARGS,T))
#endif

template<typename R BOOST_FUNCTION_COMMA
         BOOST_FUNCTION_TEMPLATE_PARMS>
class function<BOOST_FUNCTION_PARTIAL_SPEC>
  : public BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS>
{
  typedef BOOST_FUNCTION_FUNCTION<R BOOST_FUNCTION_COMMA BOOST_FUNCTION_TEMPLATE_ARGS> base_type;
  typedef function self_type;

  struct clear_type {};

public:

  function() : base_type() {}

  template<typename Functor>
  function(Functor f
#ifndef BOOST_NO_SFINAE
           ,typename enable_if_c<
                            (boost::type_traits::ice_not<
                          (is_integral<Functor>::value)>::value),
                       int>::type = 0
#endif
           ) :
    base_type(f)
  {
  }
  template<typename Functor,typename Allocator>
  function(Functor f, Allocator a
#ifndef BOOST_NO_SFINAE
           ,typename enable_if_c<
                            (boost::type_traits::ice_not<
                          (is_integral<Functor>::value)>::value),
                       int>::type = 0
#endif
           ) :
    base_type(f,a)
  {
  }

#ifndef BOOST_NO_SFINAE
  function(clear_type*) : base_type() {}
#endif

  function(const self_type& f) : base_type(static_cast<const base_type&>(f)){}

  function(const base_type& f) : base_type(static_cast<const base_type&>(f)){}

  self_type& operator=(const self_type& f)
  {
    self_type(f).swap(*this);
    return *this;
  }

  template<typename Functor>
#ifndef BOOST_NO_SFINAE
  typename enable_if_c<
                            (boost::type_traits::ice_not<
                         (is_integral<Functor>::value)>::value),
                      self_type&>::type
#else
  self_type&
#endif
  operator=(Functor f)
  {
    self_type(f).swap(*this);
    return *this;
  }

#ifndef BOOST_NO_SFINAE
  self_type& operator=(clear_type*)
  {
    this->clear();
    return *this;
  }
#endif

  self_type& operator=(const base_type& f)
  {
    self_type(f).swap(*this);
    return *this;
  }
};

#undef BOOST_FUNCTION_PARTIAL_SPEC
#endif // have partial specialization

} // end namespace boost

// Cleanup after ourselves...
#undef BOOST_FUNCTION_VTABLE
#undef BOOST_FUNCTION_COMMA
#undef BOOST_FUNCTION_FUNCTION
#undef BOOST_FUNCTION_FUNCTION_INVOKER
#undef BOOST_FUNCTION_VOID_FUNCTION_INVOKER
#undef BOOST_FUNCTION_FUNCTION_OBJ_INVOKER
#undef BOOST_FUNCTION_VOID_FUNCTION_OBJ_INVOKER
#undef BOOST_FUNCTION_FUNCTION_REF_INVOKER
#undef BOOST_FUNCTION_VOID_FUNCTION_REF_INVOKER
#undef BOOST_FUNCTION_GET_FUNCTION_INVOKER
#undef BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER
#undef BOOST_FUNCTION_GET_FUNCTION_REF_INVOKER
#undef BOOST_FUNCTION_GET_MEM_FUNCTION_INVOKER
#undef BOOST_FUNCTION_TEMPLATE_PARMS
#undef BOOST_FUNCTION_TEMPLATE_ARGS
#undef BOOST_FUNCTION_PARMS
#undef BOOST_FUNCTION_PARM
#undef BOOST_FUNCTION_ARGS
#undef BOOST_FUNCTION_ARG_TYPE
#undef BOOST_FUNCTION_ARG_TYPES
#undef BOOST_FUNCTION_VOID_RETURN_TYPE
#undef BOOST_FUNCTION_RETURN

#if defined(BOOST_MSVC)
#   pragma warning( pop )
#endif