xref: /openbsd-src/gnu/gcc/libstdc++-v3/include/tr1/functional (revision 404b540a9034ac75a6199ad1a32d1bbc7a0d4210)

// TR1 functional header -*- C++ -*-

// Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/** @file tr1/functional
 *  This is a TR1 C++ Library header.
 */

#ifndef _TR1_FUNCTIONAL
#define _TR1_FUNCTIONAL 1

#pragma GCC system_header

#include "../functional"
#include <typeinfo>
#include <tr1/type_traits>
#include <ext/type_traits.h>
#include <cstdlib>  // for std::abort
#include <tr1/tuple>

namespace std
{
_GLIBCXX_BEGIN_NAMESPACE(tr1)

  template<typename _MemberPointer>
    class _Mem_fn;

  /**
   *  @if maint
   *  Actual implementation of _Has_result_type, which uses SFINAE to
   *  determine if the type _Tp has a publicly-accessible member type
   *  result_type.
   *  @endif
  */
  template<typename _Tp>
    class _Has_result_type_helper : __sfinae_types
    {
      template<typename _Up>
      struct _Wrap_type
      { };

      template<typename _Up>
        static __one __test(_Wrap_type<typename _Up::result_type>*);

      template<typename _Up>
        static __two __test(...);

    public:
      static const bool value = sizeof(__test<_Tp>(0)) == 1;
    };

  template<typename _Tp>
    struct _Has_result_type
       : integral_constant<
           bool,
           _Has_result_type_helper<typename remove_cv<_Tp>::type>::value>
    { };

  /**
   *  @if maint
   *  If we have found a result_type, extract it.
   *  @endif
  */
  template<bool _Has_result_type, typename _Functor>
    struct _Maybe_get_result_type
    { };

  template<typename _Functor>
    struct _Maybe_get_result_type<true, _Functor>
    {
      typedef typename _Functor::result_type result_type;
    };

  /**
   *  @if maint
   *  Base class for any function object that has a weak result type, as
   *  defined in 3.3/3 of TR1.
   *  @endif
  */
  template<typename _Functor>
    struct _Weak_result_type_impl
    : _Maybe_get_result_type<_Has_result_type<_Functor>::value, _Functor>
    {
    };

  /**
   *  @if maint
   *  Strip top-level cv-qualifiers from the function object and let
   *  _Weak_result_type_impl perform the real work.
   *  @endif
  */
  template<typename _Functor>
    struct _Weak_result_type
    : _Weak_result_type_impl<typename remove_cv<_Functor>::type>
    {
    };

  template<typename _Signature>
    class result_of;

  /**
   *  @if maint
   *  Actual implementation of result_of. When _Has_result_type is
   *  true, gets its result from _Weak_result_type. Otherwise, uses
   *  the function object's member template result to extract the
   *  result type.
   *  @endif
  */
  template<bool _Has_result_type, typename _Signature>
    struct _Result_of_impl;

  // Handle member data pointers using _Mem_fn's logic
  template<typename _Res, typename _Class, typename _T1>
    struct _Result_of_impl<false, _Res _Class::*(_T1)>
    {
      typedef typename _Mem_fn<_Res _Class::*>
                ::template _Result_type<_T1>::type type;
    };

  /**
   *  @if maint
   *  Determines if the type _Tp derives from unary_function.
   *  @endif
  */
  template<typename _Tp>
    struct _Derives_from_unary_function : __sfinae_types
    {
    private:
      template<typename _T1, typename _Res>
        static __one __test(const volatile unary_function<_T1, _Res>*);

      // It's tempting to change "..." to const volatile void*, but
      // that fails when _Tp is a function type.
      static __two __test(...);

    public:
      static const bool value = sizeof(__test((_Tp*)0)) == 1;
    };

  /**
   *  @if maint
   *  Determines if the type _Tp derives from binary_function.
   *  @endif
  */
  template<typename _Tp>
    struct _Derives_from_binary_function : __sfinae_types
    {
    private:
      template<typename _T1, typename _T2, typename _Res>
        static __one __test(const volatile binary_function<_T1, _T2, _Res>*);

      // It's tempting to change "..." to const volatile void*, but
      // that fails when _Tp is a function type.
      static __two __test(...);

    public:
      static const bool value = sizeof(__test((_Tp*)0)) == 1;
    };

  /**
   *  @if maint
   *  Turns a function type into a function pointer type
   *  @endif
  */
  template<typename _Tp, bool _IsFunctionType = is_function<_Tp>::value>
    struct _Function_to_function_pointer
    {
      typedef _Tp type;
    };

  template<typename _Tp>
    struct _Function_to_function_pointer<_Tp, true>
    {
      typedef _Tp* type;
    };

  /**
   *  @if maint
   *  Knowing which of unary_function and binary_function _Tp derives
   *  from, derives from the same and ensures that reference_wrapper
   *  will have a weak result type. See cases below.
   *  @endif
   */
  template<bool _Unary, bool _Binary, typename _Tp>
    struct _Reference_wrapper_base_impl;

  // Not a unary_function or binary_function, so try a weak result type
  template<typename _Tp>
    struct _Reference_wrapper_base_impl<false, false, _Tp>
    : _Weak_result_type<_Tp>
    { };

  // unary_function but not binary_function
  template<typename _Tp>
    struct _Reference_wrapper_base_impl<true, false, _Tp>
    : unary_function<typename _Tp::argument_type,
		     typename _Tp::result_type>
    { };

  // binary_function but not unary_function
  template<typename _Tp>
    struct _Reference_wrapper_base_impl<false, true, _Tp>
    : binary_function<typename _Tp::first_argument_type,
		      typename _Tp::second_argument_type,
		      typename _Tp::result_type>
    { };

  // both unary_function and binary_function. import result_type to
  // avoid conflicts.
   template<typename _Tp>
    struct _Reference_wrapper_base_impl<true, true, _Tp>
    : unary_function<typename _Tp::argument_type,
		     typename _Tp::result_type>,
      binary_function<typename _Tp::first_argument_type,
		      typename _Tp::second_argument_type,
		      typename _Tp::result_type>
    {
      typedef typename _Tp::result_type result_type;
    };

  /**
   *  @if maint
   *  Derives from unary_function or binary_function when it
   *  can. Specializations handle all of the easy cases. The primary
   *  template determines what to do with a class type, which may
   *  derive from both unary_function and binary_function.
   *  @endif
  */
  template<typename _Tp>
    struct _Reference_wrapper_base
    : _Reference_wrapper_base_impl<
      _Derives_from_unary_function<_Tp>::value,
      _Derives_from_binary_function<_Tp>::value,
      _Tp>
    { };

  // - a function type (unary)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res(_T1)>
    : unary_function<_T1, _Res>
    { };

  // - a function type (binary)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res(_T1, _T2)>
    : binary_function<_T1, _T2, _Res>
    { };

  // - a function pointer type (unary)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res(*)(_T1)>
    : unary_function<_T1, _Res>
    { };

  // - a function pointer type (binary)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res(*)(_T1, _T2)>
    : binary_function<_T1, _T2, _Res>
    { };

  // - a pointer to member function type (unary, no qualifiers)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res (_T1::*)()>
    : unary_function<_T1*, _Res>
    { };

  // - a pointer to member function type (binary, no qualifiers)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res (_T1::*)(_T2)>
    : binary_function<_T1*, _T2, _Res>
    { };

  // - a pointer to member function type (unary, const)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res (_T1::*)() const>
    : unary_function<const _T1*, _Res>
    { };

  // - a pointer to member function type (binary, const)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const>
    : binary_function<const _T1*, _T2, _Res>
    { };

  // - a pointer to member function type (unary, volatile)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res (_T1::*)() volatile>
    : unary_function<volatile _T1*, _Res>
    { };

  // - a pointer to member function type (binary, volatile)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res (_T1::*)(_T2) volatile>
    : binary_function<volatile _T1*, _T2, _Res>
    { };

  // - a pointer to member function type (unary, const volatile)
  template<typename _Res, typename _T1>
    struct _Reference_wrapper_base<_Res (_T1::*)() const volatile>
    : unary_function<const volatile _T1*, _Res>
    { };

  // - a pointer to member function type (binary, const volatile)
  template<typename _Res, typename _T1, typename _T2>
    struct _Reference_wrapper_base<_Res (_T1::*)(_T2) const volatile>
    : binary_function<const volatile _T1*, _T2, _Res>
    { };

  template<typename _Tp>
    class reference_wrapper
      : public _Reference_wrapper_base<typename remove_cv<_Tp>::type>
    {
      // If _Tp is a function type, we can't form result_of<_Tp(...)>,
      // so turn it into a function pointer type.
      typedef typename _Function_to_function_pointer<_Tp>::type
        _M_func_type;

      _Tp* _M_data;
    public:
      typedef _Tp type;
      explicit reference_wrapper(_Tp& __indata): _M_data(&__indata)
      { }

      reference_wrapper(const reference_wrapper<_Tp>& __inref):
      _M_data(__inref._M_data)
      { }

      reference_wrapper&
      operator=(const reference_wrapper<_Tp>& __inref)
      {
        _M_data = __inref._M_data;
        return *this;
      }

      operator _Tp&() const
      { return this->get(); }

      _Tp&
      get() const
      { return *_M_data; }

#define _GLIBCXX_REPEAT_HEADER <tr1/ref_wrap_iterate.h>
#include <tr1/repeat.h>
#undef _GLIBCXX_REPEAT_HEADER
    };


  // Denotes a reference should be taken to a variable.
  template<typename _Tp>
    inline reference_wrapper<_Tp>
    ref(_Tp& __t)
    { return reference_wrapper<_Tp>(__t); }

  // Denotes a const reference should be taken to a variable.
  template<typename _Tp>
    inline reference_wrapper<const _Tp>
    cref(const _Tp& __t)
    { return reference_wrapper<const _Tp>(__t); }

  template<typename _Tp>
    inline reference_wrapper<_Tp>
    ref(reference_wrapper<_Tp> __t)
    { return ref(__t.get()); }

  template<typename _Tp>
    inline reference_wrapper<const _Tp>
    cref(reference_wrapper<_Tp> __t)
    { return cref(__t.get()); }

   template<typename _Tp, bool>
     struct _Mem_fn_const_or_non
     {
       typedef const _Tp& type;
     };

    template<typename _Tp>
      struct _Mem_fn_const_or_non<_Tp, false>
      {
        typedef _Tp& type;
      };

  template<typename _Res, typename _Class>
  class _Mem_fn<_Res _Class::*>
  {
    // This bit of genius is due to Peter Dimov, improved slightly by
    // Douglas Gregor.
    template<typename _Tp>
      _Res&
      _M_call(_Tp& __object, _Class *) const
      { return __object.*__pm; }

    template<typename _Tp, typename _Up>
      _Res&
      _M_call(_Tp& __object, _Up * const *) const
      { return (*__object).*__pm; }

    template<typename _Tp, typename _Up>
      const _Res&
      _M_call(_Tp& __object, const _Up * const *) const
      { return (*__object).*__pm; }

    template<typename _Tp>
      const _Res&
      _M_call(_Tp& __object, const _Class *) const
      { return __object.*__pm; }

    template<typename _Tp>
      const _Res&
      _M_call(_Tp& __ptr, const volatile void*) const
      { return (*__ptr).*__pm; }

    template<typename _Tp> static _Tp& __get_ref();

    template<typename _Tp>
      static __sfinae_types::__one __check_const(_Tp&, _Class*);
    template<typename _Tp, typename _Up>
      static __sfinae_types::__one __check_const(_Tp&, _Up * const *);
    template<typename _Tp, typename _Up>
      static __sfinae_types::__two __check_const(_Tp&, const _Up * const *);
    template<typename _Tp>
      static __sfinae_types::__two __check_const(_Tp&, const _Class*);
    template<typename _Tp>
      static __sfinae_types::__two __check_const(_Tp&, const volatile void*);

  public:
    template<typename _Tp>
      struct _Result_type
      : _Mem_fn_const_or_non<
        _Res,
        (sizeof(__sfinae_types::__two)
	 == sizeof(__check_const<_Tp>(__get_ref<_Tp>(), (_Tp*)0)))>
      { };

    template<typename _Signature>
      struct result;

    template<typename _CVMem, typename _Tp>
      struct result<_CVMem(_Tp)>
      : public _Result_type<_Tp> { };

    template<typename _CVMem, typename _Tp>
      struct result<_CVMem(_Tp&)>
      : public _Result_type<_Tp> { };

    explicit _Mem_fn(_Res _Class::*__pm) : __pm(__pm) { }

    // Handle objects
    _Res&       operator()(_Class& __object)       const
    { return __object.*__pm; }

    const _Res& operator()(const _Class& __object) const
    { return __object.*__pm; }

    // Handle pointers
    _Res&       operator()(_Class* __object)       const
    { return __object->*__pm; }

    const _Res&
    operator()(const _Class* __object) const
    { return __object->*__pm; }

    // Handle smart pointers and derived
    template<typename _Tp>
      typename _Result_type<_Tp>::type
      operator()(_Tp& __unknown) const
      { return _M_call(__unknown, &__unknown); }

  private:
    _Res _Class::*__pm;
  };

  /**
   *  @brief Returns a function object that forwards to the member
   *  pointer @a pm.
   */
  template<typename _Tp, typename _Class>
    inline _Mem_fn<_Tp _Class::*>
    mem_fn(_Tp _Class::* __pm)
    {
      return _Mem_fn<_Tp _Class::*>(__pm);
    }

  /**
   *  @brief Determines if the given type _Tp is a function object
   *  should be treated as a subexpression when evaluating calls to
   *  function objects returned by bind(). [TR1 3.6.1]
   */
  template<typename _Tp>
    struct is_bind_expression
    { static const bool value = false; };

  template<typename _Tp>
    const bool is_bind_expression<_Tp>::value;

  /**
   *  @brief Determines if the given type _Tp is a placeholder in a
   *  bind() expression and, if so, which placeholder it is. [TR1 3.6.2]
   */
  template<typename _Tp>
    struct is_placeholder
    { static const int value = 0; };

  template<typename _Tp>
    const int is_placeholder<_Tp>::value;

  /**
   *  @if maint
   *  The type of placeholder objects defined by libstdc++.
   *  @endif
   */
  template<int _Num> struct _Placeholder { };

  /**
   *  @if maint
   *  Partial specialization of is_placeholder that provides the placeholder
   *  number for the placeholder objects defined by libstdc++.
   *  @endif
   */
  template<int _Num>
    struct is_placeholder<_Placeholder<_Num> >
    { static const int value = _Num; };

  template<int _Num>
    const int is_placeholder<_Placeholder<_Num> >::value;

  /**
   *  @if maint
   *  Maps an argument to bind() into an actual argument to the bound
   *  function object [TR1 3.6.3/5]. Only the first parameter should
   *  be specified: the rest are used to determine among the various
   *  implementations. Note that, although this class is a function
   *  object, isn't not entirely normal because it takes only two
   *  parameters regardless of the number of parameters passed to the
   *  bind expression. The first parameter is the bound argument and
   *  the second parameter is a tuple containing references to the
   *  rest of the arguments.
   *  @endif
   */
  template<typename _Arg,
           bool _IsBindExp = is_bind_expression<_Arg>::value,
           bool _IsPlaceholder = (is_placeholder<_Arg>::value > 0)>
    class _Mu;

  /**
   *  @if maint
   *  If the argument is reference_wrapper<_Tp>, returns the
   *  underlying reference. [TR1 3.6.3/5 bullet 1]
   *  @endif
   */
  template<typename _Tp>
    class _Mu<reference_wrapper<_Tp>, false, false>
    {
    public:
      typedef _Tp& result_type;

      /* Note: This won't actually work for const volatile
       * reference_wrappers, because reference_wrapper::get() is const
       * but not volatile-qualified. This might be a defect in the TR.
       */
      template<typename _CVRef, typename _Tuple>
      result_type
      operator()(_CVRef& __arg, const _Tuple&) const volatile
      { return __arg.get(); }
    };

  /**
   *  @if maint
   *  If the argument is a bind expression, we invoke the underlying
   *  function object with the same cv-qualifiers as we are given and
   *  pass along all of our arguments (unwrapped). [TR1 3.6.3/5 bullet 2]
   *  @endif
   */
  template<typename _Arg>
    class _Mu<_Arg, true, false>
    {
    public:
      template<typename _Signature> class result;

#define _GLIBCXX_REPEAT_HEADER <tr1/mu_iterate.h>
#  include <tr1/repeat.h>
#undef _GLIBCXX_REPEAT_HEADER
    };

  /**
   *  @if maint
   *  If the argument is a placeholder for the Nth argument, returns
   *  a reference to the Nth argument to the bind function object.
   *  [TR1 3.6.3/5 bullet 3]
   *  @endif
   */
  template<typename _Arg>
    class _Mu<_Arg, false, true>
    {
    public:
      template<typename _Signature> class result;

      template<typename _CVMu, typename _CVArg, typename _Tuple>
      class result<_CVMu(_CVArg, _Tuple)>
      {
        // Add a reference, if it hasn't already been done for us.
        // This allows us to be a little bit sloppy in constructing
        // the tuple that we pass to result_of<...>.
        typedef typename tuple_element<(is_placeholder<_Arg>::value - 1),
                                       _Tuple>::type __base_type;

      public:
        typedef typename add_reference<__base_type>::type type;
      };

      template<typename _Tuple>
      typename result<_Mu(_Arg, _Tuple)>::type
      operator()(const volatile _Arg&, const _Tuple& __tuple) const volatile
      {
        return ::std::tr1::get<(is_placeholder<_Arg>::value - 1)>(__tuple);
      }
    };

  /**
   *  @if maint
   *  If the argument is just a value, returns a reference to that
   *  value. The cv-qualifiers on the reference are the same as the
   *  cv-qualifiers on the _Mu object. [TR1 3.6.3/5 bullet 4]
   *  @endif
   */
  template<typename _Arg>
    class _Mu<_Arg, false, false>
    {
    public:
      template<typename _Signature> struct result;

      template<typename _CVMu, typename _CVArg, typename _Tuple>
      struct result<_CVMu(_CVArg, _Tuple)>
      {
        typedef typename add_reference<_CVArg>::type type;
      };

      // Pick up the cv-qualifiers of the argument
      template<typename _CVArg, typename _Tuple>
      _CVArg& operator()(_CVArg& __arg, const _Tuple&) const volatile
      { return __arg; }
    };

  /**
   *  @if maint
   *  Maps member pointers into instances of _Mem_fn but leaves all
   *  other function objects untouched. Used by tr1::bind(). The
   *  primary template handles the non--member-pointer case.
   *  @endif
   */
  template<typename _Tp>
    struct _Maybe_wrap_member_pointer
    {
      typedef _Tp type;
      static const _Tp& __do_wrap(const _Tp& __x) { return __x; }
    };

  /**
   *  @if maint
   *  Maps member pointers into instances of _Mem_fn but leaves all
   *  other function objects untouched. Used by tr1::bind(). This
   *  partial specialization handles the member pointer case.
   *  @endif
   */
  template<typename _Tp, typename _Class>
    struct _Maybe_wrap_member_pointer<_Tp _Class::*>
    {
      typedef _Mem_fn<_Tp _Class::*> type;
      static type __do_wrap(_Tp _Class::* __pm) { return type(__pm); }
    };

  /**
   *  @if maint
   *  Type of the function object returned from bind().
   *  @endif
   */
   template<typename _Signature>
     struct _Bind;

  /**
   *  @if maint
   *  Type of the function object returned from bind<R>().
   *  @endif
   */
   template<typename _Result, typename _Signature>
     struct _Bind_result;

  /**
   *  @if maint
   *  Class template _Bind is always a bind expression.
   *  @endif
   */
   template<typename _Signature>
     struct is_bind_expression<_Bind<_Signature> >
     { static const bool value = true; };

   template<typename _Signature>
     const bool is_bind_expression<_Bind<_Signature> >::value;

  /**
   *  @if maint
   *  Class template _Bind_result is always a bind expression.
   *  @endif
   */
   template<typename _Result, typename _Signature>
     struct is_bind_expression<_Bind_result<_Result, _Signature> >
     { static const bool value = true; };

   template<typename _Result, typename _Signature>
     const bool is_bind_expression<_Bind_result<_Result, _Signature> >::value;

  /**
   *  @brief Exception class thrown when class template function's
   *  operator() is called with an empty target.
   *
   */
  class bad_function_call : public std::exception { };

  /**
   *  @if maint
   *  The integral constant expression 0 can be converted into a
   *  pointer to this type. It is used by the function template to
   *  accept NULL pointers.
   *  @endif
   */
  struct _M_clear_type;

  /**
   *  @if maint
   *  Trait identifying "location-invariant" types, meaning that the
   *  address of the object (or any of its members) will not escape.
   *  Also implies a trivial copy constructor and assignment operator.
   *   @endif
   */
  template<typename _Tp>
    struct __is_location_invariant
    : integral_constant<bool,
                        (is_pointer<_Tp>::value
                         || is_member_pointer<_Tp>::value)>
    {
    };

  class _Undefined_class;

  union _Nocopy_types
  {
    void*       _M_object;
    const void* _M_const_object;
    void (*_M_function_pointer)();
    void (_Undefined_class::*_M_member_pointer)();
  };

  union _Any_data {
    void*       _M_access()       { return &_M_pod_data[0]; }
    const void* _M_access() const { return &_M_pod_data[0]; }

    template<typename _Tp> _Tp& _M_access()
    { return *static_cast<_Tp*>(_M_access()); }

    template<typename _Tp> const _Tp& _M_access() const
    { return *static_cast<const _Tp*>(_M_access()); }

    _Nocopy_types _M_unused;
    char _M_pod_data[sizeof(_Nocopy_types)];
  };

  enum _Manager_operation
  {
    __get_type_info,
    __get_functor_ptr,
    __clone_functor,
    __destroy_functor
  };

  /* Simple type wrapper that helps avoid annoying const problems
     when casting between void pointers and pointers-to-pointers. */
  template<typename _Tp>
    struct _Simple_type_wrapper
    {
      _Simple_type_wrapper(_Tp __value) : __value(__value) { }

      _Tp __value;
    };

  template<typename _Tp>
    struct __is_location_invariant<_Simple_type_wrapper<_Tp> >
      : __is_location_invariant<_Tp>
    {
    };

  // Converts a reference to a function object into a callable
  // function object.
  template<typename _Functor>
    inline _Functor& __callable_functor(_Functor& __f) { return __f; }

  template<typename _Member, typename _Class>
    inline _Mem_fn<_Member _Class::*>
    __callable_functor(_Member _Class::* &__p)
    { return mem_fn(__p); }

  template<typename _Member, typename _Class>
    inline _Mem_fn<_Member _Class::*>
    __callable_functor(_Member _Class::* const &__p)
    { return mem_fn(__p); }

  template<typename _Signature, typename _Functor>
    class _Function_handler;

  template<typename _Signature>
    class function;


  /**
   *  @if maint
   *  Base class of all polymorphic function object wrappers.
   *  @endif
   */
  class _Function_base
  {
  public:
    static const std::size_t _M_max_size = sizeof(_Nocopy_types);
    static const std::size_t _M_max_align = __alignof__(_Nocopy_types);

    template<typename _Functor>
    class _Base_manager
    {
    protected:
      static const bool __stored_locally =
        (__is_location_invariant<_Functor>::value
         && sizeof(_Functor) <= _M_max_size
         && __alignof__(_Functor) <= _M_max_align
         && (_M_max_align % __alignof__(_Functor) == 0));
      typedef integral_constant<bool, __stored_locally> _Local_storage;

      // Retrieve a pointer to the function object
      static _Functor* _M_get_pointer(const _Any_data& __source)
      {
        const _Functor* __ptr =
          __stored_locally? &__source._M_access<_Functor>()
          /* have stored a pointer */ : __source._M_access<_Functor*>();
        return const_cast<_Functor*>(__ptr);
      }

      // Clone a location-invariant function object that fits within
      // an _Any_data structure.
      static void
      _M_clone(_Any_data& __dest, const _Any_data& __source, true_type)
      {
        new (__dest._M_access()) _Functor(__source._M_access<_Functor>());
      }

      // Clone a function object that is not location-invariant or
      // that cannot fit into an _Any_data structure.
      static void
      _M_clone(_Any_data& __dest, const _Any_data& __source, false_type)
      {
        __dest._M_access<_Functor*>() =
          new _Functor(*__source._M_access<_Functor*>());
      }

      // Destroying a location-invariant object may still require
      // destruction.
      static void
      _M_destroy(_Any_data& __victim, true_type)
      {
        __victim._M_access<_Functor>().~_Functor();
      }

      // Destroying an object located on the heap.
      static void
      _M_destroy(_Any_data& __victim, false_type)
      {
        delete __victim._M_access<_Functor*>();
      }

    public:
      static bool
      _M_manager(_Any_data& __dest, const _Any_data& __source,
                 _Manager_operation __op)
      {
        switch (__op) {
        case __get_type_info:
          __dest._M_access<const type_info*>() = &typeid(_Functor);
          break;

        case __get_functor_ptr:
          __dest._M_access<_Functor*>() = _M_get_pointer(__source);
          break;

        case __clone_functor:
          _M_clone(__dest, __source, _Local_storage());
          break;

        case __destroy_functor:
          _M_destroy(__dest, _Local_storage());
          break;
        }
        return false;
      }

      static void
      _M_init_functor(_Any_data& __functor, const _Functor& __f)
      {
        _M_init_functor(__functor, __f, _Local_storage());
      }

      template<typename _Signature>
      static bool
      _M_not_empty_function(const function<_Signature>& __f)
      {
        return __f;
      }

      template<typename _Tp>
      static bool
      _M_not_empty_function(const _Tp*& __fp)
      {
        return __fp;
      }

      template<typename _Class, typename _Tp>
      static bool
      _M_not_empty_function(_Tp _Class::* const& __mp)
      {
        return __mp;
      }

      template<typename _Tp>
      static bool
      _M_not_empty_function(const _Tp&)
      {
        return true;
      }

    private:
      static void
      _M_init_functor(_Any_data& __functor, const _Functor& __f, true_type)
      {
        new (__functor._M_access()) _Functor(__f);
      }

      static void
      _M_init_functor(_Any_data& __functor, const _Functor& __f, false_type)
      {
        __functor._M_access<_Functor*>() = new _Functor(__f);
      }
    };

    template<typename _Functor>
    class _Ref_manager : public _Base_manager<_Functor*>
    {
      typedef _Function_base::_Base_manager<_Functor*> _Base;

    public:
      static bool
      _M_manager(_Any_data& __dest, const _Any_data& __source,
                 _Manager_operation __op)
      {
        switch (__op) {
        case __get_type_info:
          __dest._M_access<const type_info*>() = &typeid(_Functor);
          break;

        case __get_functor_ptr:
          __dest._M_access<_Functor*>() = *_Base::_M_get_pointer(__source);
          return is_const<_Functor>::value;
          break;

        default:
          _Base::_M_manager(__dest, __source, __op);
        }
        return false;
      }

      static void
      _M_init_functor(_Any_data& __functor, reference_wrapper<_Functor> __f)
      {
        // TBD: Use address_of function instead
        _Base::_M_init_functor(__functor, &__f.get());
      }
    };

    _Function_base() : _M_manager(0) { }

    ~_Function_base()
    {
      if (_M_manager)
        {
          _M_manager(_M_functor, _M_functor, __destroy_functor);
        }
    }


    bool _M_empty() const { return !_M_manager; }

    typedef bool (*_Manager_type)(_Any_data&, const _Any_data&,
                                  _Manager_operation);

    _Any_data     _M_functor;
    _Manager_type _M_manager;
  };

  // [3.7.2.7] null pointer comparisons

  /**
   *  @brief Compares a polymorphic function object wrapper against 0
   *  (the NULL pointer).
   *  @returns @c true if the wrapper has no target, @c false otherwise
   *
   *  This function will not throw an exception.
   */
  template<typename _Signature>
    inline bool
    operator==(const function<_Signature>& __f, _M_clear_type*)
    {
      return !__f;
    }

  /**
   *  @overload
   */
  template<typename _Signature>
    inline bool
    operator==(_M_clear_type*, const function<_Signature>& __f)
    {
      return !__f;
    }

  /**
   *  @brief Compares a polymorphic function object wrapper against 0
   *  (the NULL pointer).
   *  @returns @c false if the wrapper has no target, @c true otherwise
   *
   *  This function will not throw an exception.
   */
  template<typename _Signature>
    inline bool
    operator!=(const function<_Signature>& __f, _M_clear_type*)
    {
      return __f;
    }

  /**
   *  @overload
   */
  template<typename _Signature>
    inline bool
    operator!=(_M_clear_type*, const function<_Signature>& __f)
    {
      return __f;
    }

  // [3.7.2.8] specialized algorithms

  /**
   *  @brief Swap the targets of two polymorphic function object wrappers.
   *
   *  This function will not throw an exception.
   */
  template<typename _Signature>
    inline void
    swap(function<_Signature>& __x, function<_Signature>& __y)
    {
      __x.swap(__y);
    }

_GLIBCXX_END_NAMESPACE
}

#define _GLIBCXX_JOIN(X,Y) _GLIBCXX_JOIN2( X , Y )
#define _GLIBCXX_JOIN2(X,Y) _GLIBCXX_JOIN3(X,Y)
#define _GLIBCXX_JOIN3(X,Y) X##Y
#define _GLIBCXX_REPEAT_HEADER <tr1/functional_iterate.h>
#include <tr1/repeat.h>
#undef _GLIBCXX_REPEAT_HEADER
#undef _GLIBCXX_JOIN3
#undef _GLIBCXX_JOIN2
#undef _GLIBCXX_JOIN

#include <tr1/functional_hash.h>

#endif