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Declaring functions

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Linguagem C + +
Tópicos gerais
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General topics
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Controle de fluxo
Original:
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
Original:
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
Original:
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
Original:
Specifiers
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cv especificadores
armazenamento duração especificadores
constexpr especificador (C++11)
auto especificador (C++11)
alignas especificador (C++11)
Inicialização
Original:
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)
Lança
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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
Original:
Class-specific function properties
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Funções membro especiais
Original:
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
 
Uma declaração de função introduz o nome da função e seu tipo. Pode aparecer em qualquer âmbito, e é normalmente colocada em arquivos de cabeçalho.
Original:
A function declaration introduces the function name and its type. It may appear in any scope, and is commonly placed in header files.
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ret name ( params ) ; (1)
ret name ( params ) cv ref except attr ; (2)
auto name ( params ) cv ref except attr -> ret ; (3) (a partir do C++ 11)
A definição da função fornece o corpo de uma função. Ele só pode aparecer no espaço para nome ou escopo de classe.
Original:
A function definition provides the body of a function. It may only appear in namespace or class scope.
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decl name ( params ) { body } (4)
attr decl name ( params ) cv ref except attr virt try init-list { body } catch (5)
attr decl name ( params ) cv ref except attr -> ret virt try init-list { body } catch (6) (a partir do C++ 11)
attr decl name ( params ) cv ref except attr virt = 0 ; (7)
attr decl name ( params ) cv ref except attr virt = default ; (8) (a partir do C++ 11)
attr decl name ( params ) cv ref except attr virt = delete ; (9) (a partir do C++ 11)

[editar] Explicação

1)
Declaração da função típica
Original:
Typical function declaration
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2)
Declaração da função abrangente
Original:
Comprehensive function declaration
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3)
Declaração da função abrangente com tipo de retorno à direita
Original:
Comprehensive function declaration with trailing return type
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4)
Definição de função típica não-membro
Original:
Typical non-member function definition
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5)
Definição da função global
Original:
Comprehensive function definition
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6)
Definição da função global com tipo de retorno à direita
Original:
Comprehensive function definition with trailing return type
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7)
Função membro virtual pura
Original:
Pure virtual member function
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8)
Função de membro de incumprimento
Original:
Defaulted member function
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9)
Excluídos função de membro
Original:
Deleted member function
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attr(C++11) -
Sequência opcional de qualquer número de atributos de função, como [[noreturn]] ou [[carries_dependency]]. Pode aparecer tanto antes como depois do nome de função
Original:
Optional sequence of any number of atributos de função, such as [[noreturn]] or [[carries_dependency]]. May appear both before and after the function name
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ret -
o tipo retornado pela função, pode ser void se a função retorna nada. Não pode ser matriz ou tipo de função, embora possa ser um ponteiro ou referência a tal. Obrigatório para todas as funções, exceto os construtores, destrutores e operadores de conversão, o que não deve fornecer um tipo de retorno .
Original:
the type returned by the function, may be void if the function returns nothing. Cannot be array or function type, although can be a pointer or reference to such. Required for all functions except constructors, destructors, and conversion operators, which must not provide a return type.
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decl -
declaração seqüência especificador, que consiste em nenhum ou alguns dos seguintes palavras-chave: externo, estático, inline, virtual, explicit, friend, constexpr, combinado com o tipo de retorno, ret
Original:
declaration specifier sequence, which consists of none or some of the following keywords: externo, estático, inline, virtual, explicit, friend, constexpr, combined with the return type, ret
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{{par | cv |{{tr| Opcional const, volatile, ou const volatile, só aplicável às funções não-estáticos membros. Para uma função membro da classe T, o tipo de [[CPP / linguagem / isso| Optional const, volatile, or const volatile, only applicable to non-static member functions. For a member function of class T, the type of the [[cpp/language/this}}|this pointer]] will be const T*, volatile T*, or const volatile T* respectively. A member function declared const cannot modify members of *this.}}

ref(C++11) -
Opcional & ou &&, só aplicável às funções não-estáticos-Membro diferente construtores ou destruidores. Para uma função de membro de T classe, o tipo do parâmetro objeto implícito com o propósito de resolução de sobrecarga será T& ou T&& respectivamente: a função membro && qualificado só pode ser chamado em uma expressão de objeto rvalue
Original:
Optional & or &&, only applicable to non-static member functions other than constructors or destructors. For a member function of class T, the type of the implicit object parameter for the purpose of overload resolution will be T& or T&& respectively: a &&-qualified member function can only be called on an rvalue object expression
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except -
ou dinâmico exceção especificação ou noexcept-especificação
Original:
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virt(C++11) -
Opcional override ou final, só aplicável às funções não-estáticos membros
Original:
Optional override or final, only applicable to non-static member functions
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->ret(C++11) -
Trailing tipo de retorno, só se aplica se ret é auto. É útil se o tipo depende nomes de argumento, tais como template <class T, class U> auto add(T t, U u) -> decltype(t + u); ou é complicado, como em auto fpif(int)->int(*)(int)
Original:
Trailing return type, only applicable if ret is auto. Useful if the type depends on argument names, such as template <class T, class U> auto add(T t, U u) -> decltype(t + u); or is complicated, such as in auto fpif(int)->int(*)(int)
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init-list -
Lista de inicializador construtor, utilizado de construtores
Original:
Lista de inicializador construtor, only used in constructors
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try -
Bloco try opcional função. Se estiver presente, catch deve ser fornecido
Original:
Optional function try block. If present, catch must be provided
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catch -
Seqüência opcional de pegá-blocos, aplicável apenas de try é usado .
Original:
Optional sequence of pegá-blocos, only applicable of try is used.
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body -
O corpo da função, um comando composto (possivelmente vazio)
Original:
The body of the function, a (possibly empty) compound statement
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params -
A lista de parâmetros
Original:
The list of parameters
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[editar] Exemplo 1: não-membros funções

#include <iostream>
#include <string>
 
// declaration in namespace(file) scope
// (the definition is provided later)
int f1();
 
// simple function with a default argument, returning nothing
void f0(const std::string& arg = "world") {
    std::cout << "Hello, " << arg << '\n';
}
 
// function returning a pointer to f0
auto fp11() -> void(*)(const std::string&) {
    return f0;
}
 
// function returning a pointer to f0, pre-C++11 style
void (*fp03())(const std::string&) {
    return f0;
}
 
int main()
{
    f0();
    fp11()("test");
    fp03()("again");
    int f2(std::string); // declaration in function scope
    std::cout << f2("bad12") << '\n';
}
 
// simple non-member function returning int
int f1() {
    return 42;
}
 
// function with an exception specification and a function try block
int f2(std::string str) noexcept try { 
    return std::stoi(str);
} catch(const std::exception& e) {
    std::cerr << "stoi() failed!\n";
    return 0;
}

Output:

Hello, world
Hello, test
Hello, again
stoi() failed!
0


[editar] Exemplo 2: funções de membro

#include <iostream>
#include <string>
#include <utility>
#include <exception>
 
struct S {
    int data;
 
    // simple converting constructor (declaration)
    S(int val);
 
    // simple explicit constructor (declaration)
    explicit S(std::string str);
 
    // const member function (definition)
    virtual int getData() const { return data; }
 
};
 
// definition of the constructor
S::S(int val) : data(val) {
    std::cout << "ctor1 called, data = " << data << '\n';
}
 
// this constructor has a catch clause
S::S(std::string str) try : data(std::stoi(str)) {
    std::cout << "ctor2 called, data = " << data << '\n';
} catch(const std::exception&) {
    std::cout << "ctor2 failed, string was '" << str << "'\n";
    throw; // ctor's catch clause should always rethrow
}
 
struct D : S {
    int data2;
    // constructor with a default argument
    D(int v1, int v2 = 11) : S(v1), data2(v2) {}
 
    // virtual member function
    int getData() const override { return data*data2; }
 
    // lvalue-only assignment operator
    D& operator=(D other) & {
        std::swap(other.data, data);
        std::swap(other.data2, data2);
        return *this;
    }
};
 
int main()
{
    D d1 = 1;
    S s2("2");
    try {
         S s3("not a number");
    } catch(const std::exception&) {}
    std::cout << s2.getData() << '\n';
 
   D d2(3, 4);
   d2 = d1; // OK: assignment to lvalue
//   D(5) = d1; // ERROR: no suitable overload of operator=
}

Output:

ctor1 called, data = 1
ctor2 called, data = 2
ctor2 failed, string was 'not a number'
2
ctor1 called, data = 3