std::integral_constant

 

C++

Suporte ao Compilador

Freestanding and hosted

Linguagem

Headers da Biblioteca Standard

Requerimentos nomeados

Feature test macros (C++20)

Biblioteca de suporte de língua

Biblioteca de conceitos (C++20)

Biblioteca de diagnósticos

Biblioteca de utilitários em geral

Biblioteca de strings

Biblioteca de containers

Ranges library (C++20)

Biblioteca de iteradores

Biblioteca de algorítmos

Biblioteca numérica

Biblioteca de localizações

Biblioteca de input/output

Biblioteca de sistema de arquivo (C++17)

Biblioteca de expressões regulares (C++11)

Biblioteca de operações atômicas (C++11)

Biblioteca de suporte de thread (C++11)

Especificações Técnicas

Índice de symbolos

Bibliotecas externas

 

Biblioteca de utilitários

Digite apoio (basic types, RTTI, type traits)

Gerenciamento de memória dinâmica

De tratamento de erros

Utilidades do programa

Variadic funções

Data e hora

Objetos de função

initializer_list (C++11)

bitset

hash (C++11)

Os operadores relacionais Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pares e tuplas Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Troque, avançar e avançar Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Apoio a tipos

Tipos básicos Original: Basic types The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Tipos fundamentais
Tipos inteiros de largura fixos (C++11)
ptrdiff_t size_t max_align_t (C++11)	nullptr_t (C++11) offsetof NULL
Limites numéricos Original: Numeric limits The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
numeric_limits
C numérico limita interface
Informações de tipo de tempo de execução Original: Runtime type information The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
type_info type_index (C++11)	bad_typeid bad_cast
Características de tipo Original: Type traits The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Principais categorias de tipo Original: Primary type categories The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_void (C++11) is_array (C++11) is_pointer (C++11) is_enum (C++11) is_union (C++11) is_class (C++11) is_function (C++11)	is_object (C++11) is_scalar (C++11) is_compound (C++11) is_integral (C++11) is_floating_point (C++11) is_fundamental (C++11) is_arithmetic (C++11)
is_reference (C++11)
is_lvalue_reference (C++11)
is_rvalue_reference (C++11)
is_member_pointer (C++11)
is_member_object_pointer (C++11)
is_member_function_pointer (C++11)

Propriedades de tipo Original: Type properties The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_const (C++11) is_volatile (C++11) is_pod (C++11) is_empty (C++11) is_polymorphic (C++11) is_abstract (C++11)	is_trivial (C++11) is_trivially_copyable (C++11) is_standard_layout (C++11) is_literal_type (C++11) is_signed (C++11) is_unsigned (C++11)

Operações apoiadas Original: Supported operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_constructibleis_trivially_constructibleis_nothrow_constructible (C++11)(C++11)(C++11)
is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible (C++11)(C++11)(C++11)
is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible (C++11)(C++11)(C++11)
is_move_constructibleis_trivially_move_constructibleis_nothrow_move_constructible (C++11)(C++11)(C++11)
is_assignableis_trivially_assignableis_nothrow_assignable (C++11)(C++11)(C++11)
is_copy_assignableis_trivially_copy_assignableis_nothrow_copy_assignable (C++11)(C++11)(C++11)
is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable (C++11)(C++11)(C++11)
is_destructibleis_trivially_destructibleis_nothrow_destructible (C++11)(C++11)(C++11)
has_virtual_destructor (C++11)
Relacionamentos e consultas de propriedade Original: Relationships and property queries The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_same (C++11) is_base_of (C++11) is_convertible (C++11)	alignment_of (C++11) rank (C++11) extent (C++11)
Tipo modificações Original: Type modifications The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
remove_cvremove_constremove_volatile (C++11)(C++11)(C++11) add_cvadd_constadd_volatile (C++11)(C++11)(C++11) make_signed (C++11) make_unsigned (C++11)	remove_reference (C++11) add_lvalue_referenceadd_rvalue_reference (C++11)(C++11) remove_pointer (C++11) add_pointer (C++11) remove_extent (C++11) remove_all_extents (C++11)
Transformações tipo Original: Type transformations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
aligned_storage (C++11) aligned_union (C++11) decay (C++11) enable_if (C++11)	conditional (C++11) common_type (C++11) underlying_type (C++11) result_of (C++11)
Digite constantes traço Original: Type trait constants The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
integral_constant (C++11)

 

Definido no cabeçalho <type_traits>
template< class T, T v > struct integral_constant;		(desde C++11)

std::integral_constant envolve uma constante estática do tipo especificado. É a classe base para o C + + características de tipo.

Original:

std::integral_constant wraps a static constant of specified type. It is the base class for the C++ type traits.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Duas especializações para o bool tipo são fornecidos:

Original:

Two specializations for the type bool are provided:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Defined in header <type_traits>
Tipo Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Definition
true_type	std::integral_constant<bool, true>
false_type	std::integral_constant<bool, false>

Tipos de membro

Tipo Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Definition
value_type	T
type	std::integral_constant<T,v>

Constantes de membros

Nome Original: Name The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Value
value	expressão constante estática de T tipo com v valor Original: static constant expression of type T with value v The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Funções de membro

operator value_type	converte o objeto em value_type, retorna value Original: converts the object to value_type, returns value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro)

Possível implementação

template<class T, T v> struct integral_constant { static constexpr T value = v; typedef T value_type; typedef integral_constant type; constexpr operator value_type() const { return value; } };

Exemplo

#include <iostream>
#include <type_traits>
 
int main() 
{
    typedef std::integral_constant<int, 2> two_t;
    typedef std::integral_constant<int, 4> four_t;
 
//  static_assert(std::is_same<two_t, four_t>::value,
//                "two_t and four_t are not equal!"); 
//  error: static assertion failed: "two_t and four_t are not a same types"
 
    static_assert(two_t::value*2 == four_t::value,
       "2*2 != 4"
    );
 
    enum class my_e {
       e1,
       e2
    };
    typedef std::integral_constant<my_e, my_e::e1> my_e_e1;
    typedef std::integral_constant<my_e, my_e::e2> my_e_e2;
 
//  static_assert(my_e_e1::value == my_e::e2,
//               "my_e_e1::value != my_e::e2");
//  error: static assertion failed: "my_e_e1::value != my_e::e2"
 
    static_assert(std::is_same<my_e_e2, my_e_e2>::value,
                  "my_e_e2 != my_e_e2");
}