type_traits

Go to the documentation of this file.

// TR1 type_traits -*- C++ -*-

// Copyright (C) 2004, 2005 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// 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 
 *  This is a TR1 C++ Library header. 
 */

#ifndef _TYPE_TRAITS
#define _TYPE_TRAITS 1

#include <bits/c++config.h>
#include <tr1/type_traits_fwd.h>

// namespace std::tr1
namespace std
{
namespace tr1
{
  // For use in __conv_helper, is_abstract and elsewhere.
  struct __sfinae_types
  {
    typedef char __one;
    typedef struct { char __arr[2]; } __two;
  };

  template<typename _From, typename _To>
    struct __conv_helper
    : public __sfinae_types
    {
    private:
      static __one __test(_To);
      static __two __test(...);
      static _From __makeFrom();
    
    public:
      static const bool __value = sizeof(__test(__makeFrom())) == 1;
    };

#define _DEFINE_SPEC_BODY(_Value)                                    \
    : public integral_constant<bool, _Value> { };

#define _DEFINE_SPEC_0_HELPER(_Spec, _Value)                         \
  template<>                                                         \
    struct _Spec                                                     \
    _DEFINE_SPEC_BODY(_Value)

#define _DEFINE_SPEC_1_HELPER(_Spec, _Value)                         \
  template<typename _Tp>                                             \
    struct _Spec                                                     \
    _DEFINE_SPEC_BODY(_Value)
      
#define _DEFINE_SPEC_2_HELPER(_Spec, _Value)                         \
  template<typename _Tp, typename _Cp>                               \
    struct _Spec                                                     \
    _DEFINE_SPEC_BODY(_Value)

#define _DEFINE_SPEC(_Order, _Trait, _Type, _Value)                  \
  _DEFINE_SPEC_##_Order##_HELPER(_Trait<_Type>, _Value)              \
  _DEFINE_SPEC_##_Order##_HELPER(_Trait<_Type const>, _Value)        \
  _DEFINE_SPEC_##_Order##_HELPER(_Trait<_Type volatile>, _Value)     \
  _DEFINE_SPEC_##_Order##_HELPER(_Trait<_Type const volatile>, _Value)

  /// @brief  helper classes [4.3].
  template<typename _Tp, _Tp __v>
    struct integral_constant
    {
      static const _Tp                      value = __v;
      typedef _Tp                           value_type;
      typedef integral_constant<_Tp, __v>   type;
    };
  typedef integral_constant<bool, true>     true_type;
  typedef integral_constant<bool, false>    false_type;

  /// @brief  primary type categories [4.5.1].
  template<typename>
    struct is_void
    : public false_type { };
  _DEFINE_SPEC(0, is_void, void, true)

  template<typename>
    struct is_integral
    : public false_type { };
  _DEFINE_SPEC(0, is_integral, bool, true)
  _DEFINE_SPEC(0, is_integral, char, true)
  _DEFINE_SPEC(0, is_integral, signed char, true)
  _DEFINE_SPEC(0, is_integral, unsigned char, true)
#ifdef _GLIBCXX_USE_WCHAR_T
  _DEFINE_SPEC(0, is_integral, wchar_t, true)
#endif
  _DEFINE_SPEC(0, is_integral, short, true)
  _DEFINE_SPEC(0, is_integral, unsigned short, true)
  _DEFINE_SPEC(0, is_integral, int, true)
  _DEFINE_SPEC(0, is_integral, unsigned int, true)
  _DEFINE_SPEC(0, is_integral, long, true)
  _DEFINE_SPEC(0, is_integral, unsigned long, true)
  _DEFINE_SPEC(0, is_integral, long long, true)
  _DEFINE_SPEC(0, is_integral, unsigned long long, true)

  template<typename>
    struct is_floating_point
    : public false_type { };
  _DEFINE_SPEC(0, is_floating_point, float, true)
  _DEFINE_SPEC(0, is_floating_point, double, true)
  _DEFINE_SPEC(0, is_floating_point, long double, true)

  template<typename>
    struct is_array
    : public false_type { };

  template<typename _Tp, std::size_t _Size>
    struct is_array<_Tp[_Size]>
    : public true_type { };

  template<typename _Tp>
    struct is_array<_Tp[]>
    : public true_type { };

  template<typename>
    struct is_pointer
    : public false_type { };
  _DEFINE_SPEC(1, is_pointer, _Tp*, true)
 
  template<typename>
    struct is_reference
    : public false_type { };

  template<typename _Tp>
    struct is_reference<_Tp&>
    : public true_type { };

  template<typename>
    struct is_member_object_pointer
    : public false_type { };
  _DEFINE_SPEC(2, is_member_object_pointer, _Tp _Cp::*,
           !is_function<_Tp>::value)

  template<typename>
    struct is_member_function_pointer
    : public false_type { };
  _DEFINE_SPEC(2, is_member_function_pointer, _Tp _Cp::*,
           is_function<_Tp>::value)

  template<typename _Tp>
    struct is_enum
    : public integral_constant<bool, !(is_fundamental<_Tp>::value
                       || is_array<_Tp>::value
                       || is_pointer<_Tp>::value
                       || is_reference<_Tp>::value
                       || is_member_pointer<_Tp>::value
                       || is_function<_Tp>::value
                       || __is_union_or_class<_Tp>::value)>
    { };

  template<typename>
    struct is_union { };

  template<typename>
    struct is_class { };

  template<typename _Tp, bool = (is_void<_Tp>::value
                 || is_reference<_Tp>::value)>
    struct __is_function_helper
    {
      static const bool __value = (__conv_helper<typename
                   add_reference<_Tp>::type, typename
                   add_pointer<_Tp>::type>::__value);
    };

  template<typename _Tp>
    struct __is_function_helper<_Tp, true>
    { static const bool __value = false; };

  template<typename _Tp>
    struct is_function
    : public integral_constant<bool, __is_function_helper<_Tp>::__value>
    { };

  /// @brief  composite type traits [4.5.2].
  template<typename _Tp>
    struct is_arithmetic
    : public integral_constant<bool, (is_integral<_Tp>::value
                      || is_floating_point<_Tp>::value)>
    { };

  template<typename _Tp>
    struct is_fundamental
    : public integral_constant<bool, (is_arithmetic<_Tp>::value
                      || is_void<_Tp>::value)>
    { };

  template<typename _Tp>
    struct is_object
    : public integral_constant<bool, !(is_function<_Tp>::value
                       || is_reference<_Tp>::value
                       || is_void<_Tp>::value)>
    { };

  template<typename _Tp>
    struct is_scalar
    : public integral_constant<bool, (is_arithmetic<_Tp>::value
                      || is_enum<_Tp>::value
                      || is_pointer<_Tp>::value
                      || is_member_pointer<_Tp>::value)>
    { };

  template<typename _Tp>
    struct is_compound
    : public integral_constant<bool, !is_fundamental<_Tp>::value> { };

  template<typename _Tp>
    struct is_member_pointer
    : public integral_constant<bool,
                   (is_member_object_pointer<_Tp>::value
                || is_member_function_pointer<_Tp>::value)>
    { };

  template<typename _Tp>
    struct __is_union_or_class_helper
    : public __sfinae_types
    {
    private:
      template<typename _Up>
        static __one __test(int _Up::*);
      template<typename>
        static __two __test(...);
    
    public:
      static const bool __value = sizeof(__test<_Tp>(0)) == 1;
    };

  // Extension.
  template<typename _Tp>
    struct __is_union_or_class
    : public integral_constant<bool, __is_union_or_class_helper<_Tp>::__value>
    { };
  
  /// @brief  type properties [4.5.3].
  template<typename>
    struct is_const
    : public false_type { };

  template<typename _Tp>
    struct is_const<_Tp const>
    : public true_type { };
  
  template<typename>
    struct is_volatile
    : public false_type { };

  template<typename _Tp>
    struct is_volatile<_Tp volatile>
    : public true_type { };

  template<typename _Tp>
    struct is_pod
    : public integral_constant<bool, (is_void<_Tp>::value
                      || is_scalar<typename
                      remove_all_extents<_Tp>::type>::value)>
    { };

  // N.B. Without compiler support we cannot tell union from class types,
  // and is_empty and is_polymorphic don't work at all with the former. 
  template<typename _Tp, bool = !__is_union_or_class<_Tp>::value>
    struct __is_empty_helper
    { 
    private:
      template<typename>
        struct __first { };
      template<typename _Up>
        struct __second
        : public _Up { };
           
    public:
      static const bool __value = sizeof(__first<_Tp>) == sizeof(__second<_Tp>);
    };

  template<typename _Tp>
    struct __is_empty_helper<_Tp, true>
    { static const bool __value = false; };

  template<typename _Tp>
    struct is_empty
    : public integral_constant<bool, __is_empty_helper<_Tp>::__value>
    { };

  template<typename _Tp, bool = !__is_union_or_class<_Tp>::value>
    struct __is_polymorphic_helper
    { 
    private:
      template<typename _Up>
        struct __first
        : public _Up { };
      template<typename _Up>
        struct __second
        : public _Up
    { 
      virtual void __dummy();
      virtual ~__second();
    };

    public:
      static const bool __value = sizeof(__first<_Tp>) == sizeof(__second<_Tp>);
    };

  template<typename _Tp>
    struct __is_polymorphic_helper<_Tp, true>
    { static const bool __value = false; };

  template<typename _Tp>
    struct is_polymorphic
    : public integral_constant<bool, __is_polymorphic_helper<_Tp>::__value>
    { };

  // Exploit the resolution DR core/337.
  template<typename _Tp, bool = !is_object<_Tp>::value>
    struct __is_abstract_helper
    : public __sfinae_types
    {
    private:
      template<typename>
        static __one __test(...);
      template<typename _Up>
        static __two __test(_Up(*)[1]);
    
    public:
      static const bool __value = sizeof(__test<_Tp>(0)) == 1;
    };
  
  template<typename _Tp>
    struct __is_abstract_helper<_Tp, true>
    { static const bool __value = false; };

  template<typename _Tp>
    struct is_abstract
    : public integral_constant<bool, __is_abstract_helper<_Tp>::__value> { };

  template<typename _Tp>
    struct has_trivial_constructor
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_trivial_copy
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_trivial_assign
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_trivial_destructor
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_nothrow_constructor
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_nothrow_copy
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename _Tp>
    struct has_nothrow_assign
    : public integral_constant<bool, is_pod<_Tp>::value> { };

  template<typename>
    struct has_virtual_destructor
    : public false_type { };

  template<typename>
    struct is_signed
    : public false_type { };
  _DEFINE_SPEC(0, is_signed, signed char, true)
  _DEFINE_SPEC(0, is_signed, short, true)
  _DEFINE_SPEC(0, is_signed, int, true)
  _DEFINE_SPEC(0, is_signed, long, true)
  _DEFINE_SPEC(0, is_signed, long long, true)

  template<typename>
    struct is_unsigned
    : public false_type { };
  _DEFINE_SPEC(0, is_unsigned, unsigned char, true)
  _DEFINE_SPEC(0, is_unsigned, unsigned short, true)
  _DEFINE_SPEC(0, is_unsigned, unsigned int, true)
  _DEFINE_SPEC(0, is_unsigned, unsigned long, true)
  _DEFINE_SPEC(0, is_unsigned, unsigned long long, true)

  template<typename _Tp>
    struct alignment_of
    : public integral_constant<std::size_t, __alignof__(_Tp)> { };
  
  template<typename>
    struct rank
    : public integral_constant<std::size_t, 0> { };
   
  template<typename _Tp, std::size_t _Size>
    struct rank<_Tp[_Size]>
    : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };

  template<typename _Tp>
    struct rank<_Tp[]>
    : public integral_constant<std::size_t, 1 + rank<_Tp>::value> { };
   
  template<typename, unsigned>
    struct extent
    : public integral_constant<std::size_t, 0> { };
  
  template<typename _Tp, unsigned _Uint, std::size_t _Size>
    struct extent<_Tp[_Size], _Uint>
    : public integral_constant<std::size_t,
                   _Uint == 0 ? _Size : extent<_Tp,
                               _Uint - 1>::value>
    { };

  template<typename _Tp, unsigned _Uint>
    struct extent<_Tp[], _Uint>
    : public integral_constant<std::size_t,
                   _Uint == 0 ? 0 : extent<_Tp,
                               _Uint - 1>::value>
    { };
  
  /// @brief  relationships between types [4.6].
  template<typename, typename>
    struct is_same
    : public false_type { };

  template<typename _Tp>
    struct is_same<_Tp, _Tp>
    : public true_type { };

  // See Daveed Vandevoorde explanation in http://tinyurl.com/502f.
  // Also see Rani Sharoni in http://tinyurl.com/6jvyq.
  template<typename _Base, typename _Derived,
       bool = (!__is_union_or_class<_Base>::value
           || !__is_union_or_class<_Derived>::value
           || is_same<_Base, _Derived>::value)>
    struct __is_base_of_helper
    : public __sfinae_types
    {
    private:
      typedef typename remove_cv<_Base>::type     _NoCv_Base;      
      typedef typename remove_cv<_Derived>::type  _NoCv_Derived;
      
      template<typename _Up>
        static __one __test(_NoCv_Derived&, _Up);
      static __two __test(_NoCv_Base&, int);
   
      struct _Conv
      {
    operator _NoCv_Derived&();
    operator _NoCv_Base&() const;
      };
   
    public:
      static const bool __value = sizeof(__test(_Conv(), 0)) == 1;
    };

  template<typename _Base, typename _Derived>
    struct __is_base_of_helper<_Base, _Derived, true>
    { static const bool __value = is_same<_Base, _Derived>::value; };

  template<typename _Base, typename _Derived>
    struct is_base_of
    : public integral_constant<bool,
                   __is_base_of_helper<_Base, _Derived>::__value>
    { };

  template<typename _Tp>
    struct __is_int_or_cref
    {
      typedef typename remove_reference<_Tp>::type __rr_Tp;
      static const bool __value = (is_integral<_Tp>::value
                   || (is_integral<__rr_Tp>::value
                       && is_const<__rr_Tp>::value
                       && !is_volatile<__rr_Tp>::value));
    };

  template<typename _From, typename _To,
       bool = (is_function<_To>::value || is_array<_To>::value
           // This special case is here only to avoid warnings.        
           || (is_floating_point<typename
               remove_reference<_From>::type>::value
               && __is_int_or_cref<_To>::__value))>
    struct __is_convertible_helper
    {
      // "An imaginary lvalue of type From...".
      static const bool __value = (__conv_helper<typename
                   add_reference<_From>::type, _To>::__value);
    };

  template<typename _From, typename _To>
    struct __is_convertible_helper<_From, _To, true>
    { static const bool __value = __is_int_or_cref<_To>::__value; };

  template<typename _From, typename _To>
    struct is_convertible
    : public integral_constant<bool,
                   __is_convertible_helper<_From, _To>::__value>
    { };

  /// @brief  const-volatile modifications [4.7.1].
  template<typename _Tp>
    struct remove_const
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_const<_Tp const>
    { typedef _Tp     type; };
  
  template<typename _Tp>
    struct remove_volatile
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_volatile<_Tp volatile>
    { typedef _Tp     type; };
  
  template<typename _Tp>
    struct remove_cv
    {
      typedef typename
      remove_const<typename remove_volatile<_Tp>::type>::type     type;
    };
  
  template<typename _Tp>
    struct add_const
    { typedef _Tp const     type; };
   
  template<typename _Tp>
    struct add_volatile
    { typedef _Tp volatile     type; };
  
  template<typename _Tp>
    struct add_cv
    {
      typedef typename
      add_const<typename add_volatile<_Tp>::type>::type     type;
    };

  /// @brief  reference modifications [4.7.2].
  template<typename _Tp>
    struct remove_reference
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_reference<_Tp&>
    { typedef _Tp     type; };
  
  template<typename _Tp>
    struct add_reference
    { typedef _Tp&    type; };

  template<typename _Tp>
    struct add_reference<_Tp&>
    { typedef _Tp&    type; };

  /// @brief  array modififications [4.7.3].
  template<typename _Tp>
    struct remove_extent
    { typedef _Tp     type; };

  template<typename _Tp, std::size_t _Size>
    struct remove_extent<_Tp[_Size]>
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_extent<_Tp[]>
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_all_extents
    { typedef _Tp     type; };

  template<typename _Tp, std::size_t _Size>
    struct remove_all_extents<_Tp[_Size]>
    { typedef typename remove_all_extents<_Tp>::type     type; };

  template<typename _Tp>
    struct remove_all_extents<_Tp[]>
    { typedef typename remove_all_extents<_Tp>::type     type; };

  /// @brief  pointer modifications [4.7.4].
#undef _DEFINE_SPEC_BODY
#define _DEFINE_SPEC_BODY(_Value)      \
    { typedef _Tp     type; };

  template<typename _Tp>
    struct remove_pointer
    { typedef _Tp     type; };
  _DEFINE_SPEC(1, remove_pointer, _Tp*, false)
  
  template<typename _Tp>
    struct add_pointer
    { typedef typename remove_reference<_Tp>::type*     type; };

  /// @brief  other transformations [4.8].
  
  // Due to c++/19163 and c++/17743, for the time being we cannot use
  // the correct, neat implementation :-(
  // 
  // template<std::size_t _Len, std::size_t _Align>
  //   struct aligned_storage
  //   { typedef char type[_Len] __attribute__((__aligned__(_Align))); }
  //
  // Temporary workaround, useful for Align up to 32:
  template<std::size_t, std::size_t>
    struct aligned_storage { };

  template<std::size_t _Len>
    struct aligned_storage<_Len, 1>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(1)));
      };
    };

  template<std::size_t _Len>
    struct aligned_storage<_Len, 2>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(2)));
      };
    };

  template<std::size_t _Len>
    struct aligned_storage<_Len, 4>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(4)));
      };
    };

  template<std::size_t _Len>
    struct aligned_storage<_Len, 8>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(8)));
      };
    };

  template<std::size_t _Len>
    struct aligned_storage<_Len, 16>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(16)));
      };
    };
  
  template<std::size_t _Len>
    struct aligned_storage<_Len, 32>
    {
      union type
      {
    unsigned char __data[_Len];
    char __align __attribute__((__aligned__(32)));
      };
    };

#undef _DEFINE_SPEC_0_HELPER
#undef _DEFINE_SPEC_1_HELPER
#undef _DEFINE_SPEC_2_HELPER
#undef _DEFINE_SPEC
#undef _DEFINE_SPEC_BODY

}
}

#endif

---