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Union declaration

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C++
 
Linguagem C++
Tópicos gerais
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General topics
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Controle de fluxo
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Flow control
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Declarações execução condicional
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Conditional execution statements
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Instruções de iteração
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Iteration statements
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Ir declarações
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Jump statements
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Funções
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Functions
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declaração da função
lambda declaração da função
modelo de função
linha especificador
especificações de exceção (obsoleta)
noexcept especificador (C++11)
Exceções
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Exceptions
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Namespaces
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Namespaces
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Tipos
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Types
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tipos de união
tipos de função
decltype specifier (C++11)
Especificadores
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Specifiers
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cv especificadores
armazenamento duração especificadores
constexpr especificador (C++11)
auto especificador (C++11)
alignas especificador (C++11)
Inicialização
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Initialization
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Literais
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Literals
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Expressões
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Expressions
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representações alternativas
Utilitários
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Utilities
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Tipos
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Types
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typedef declaration
tipo de alias declaração (C++11)
atributos (C++11)
Conversões
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Casts
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conversões implícitas
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
Elenco C-estilo e funcional
Alocação de memória
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Memory allocation
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Classes
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Classes
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Classe propriedades específicas de função
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Class-specific function properties
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Funções membro especiais
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Special member functions
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Modelos
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Templates
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modelo de classe
modelo de função
especialização de modelo
pacotes de parâmetros (C++11)
Diversos
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Miscellaneous
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Assembly embutido
 
Esta seção está incompleta
Motivo: Expand description and example
Uma união é um tipo de classe especial que armazena todos os seus membros de dados no mesmo local da memória.
Original:
A union is a special class type that stores all of its data members in the same memory location.
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Os sindicatos não podem ter funções virtuais, ser herdado ou herdar de outras classes.
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Unions cannot have virtual functions, be inherited or inherit other classes.
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Sindicatos (até C++11) só pode conter tipos POD (plain dados antigos).
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(até C++11) Unions can only contain POD (plain dados antigos) types.
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(desde C++11) Se uma união contém um membro não-POD, que tem uma função definida pelo usuário especial (construtor, destruidor construtor de cópia, ou de atribuição de cópia) que a função é excluído por padrão na união e precisa ser definida explicitamente pelo usuário.
Original:
(desde C++11) If a union contains a non-POD member, which has a user-defined special function (constructor, destructor, copy constructor or copy assignment) that function is deleted by default in the union and needs to be defined explicitly by the user.
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Índice

[editar] Sintaxe

union name { member_declarations } object_list (opcional) ; (1)
union { member_declarations } ; (2)

[editar] Explicação

# Chamado união
Original:
#Named union
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União # Anonymous
Original:
#Anonymous union
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[editar] Sindicatos anônimos

Membros de uma união anônima são acessíveis a partir do escopo encerrar, como as variáveis ​​simples.
Original:
Members of an anonymous union are accessible from the enclosing scope as single variables.
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Sindicatos anônimos têm mais restrições: eles devem ter apenas os membros públicos e não pode ter funções membro.
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Anonymous unions have further restrictions: they must have only public members and cannot have member functions.
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Namespace de escopo de sindicatos anônimos deve ser estático.
Original:
Namespace-scope anonymous unions must be static.
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[editar] Exemplo

union foo
{
  int x;
  signed char y;
};
 
int main()
{
  foo.x = 128 + 896;
  std::cout << "as int: "  << (int)foo.x << '\n';
  std::cout << "as char: " << (int)foo.y << '\n';
  return 0;
}

Saída: 

as int: 1024
as char: 128
(Para little-endian processadores)
Original:
(for little-endian processors)
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