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std::basic_ios::operator bool

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< cpp‎ | io‎ | basic ios

 
 
De entrada / saída da biblioteca
I / O manipuladores
C estilo de I / O
Buffers
Original:
Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf(obsoleta)
Streams
Original:
Streams
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Abstrações
Original:
Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I / O
Original:
File I/O
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basic_ifstream
basic_ofstream
basic_fstream
Cordas I / O
Original:
String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
Matriz de I / O
Original:
Array I/O
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istrstream(obsoleta)
ostrstream(obsoleta)
strstream(obsoleta)
Tipos
Original:
Types
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streamoff
streamsize
fpos
Interface de categoria de erro
Original:
Error category interface
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iostream_category(C++11)
io_errc(C++11)
 
std::basic_ios
Funções de membro
Original:
Member functions
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basic_ios::basic_ios
basic_ios::~basic_ios
Funções do Estado
Original:
State functions
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basic_ios::good
basic_ios::eof
basic_ios::fail
basic_ios::bad
basic_ios::operator!
basic_ios::operator bool
basic_ios::rdstate
basic_ios::setstate
basic_ios::clear
Formatação
Original:
Formatting
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basic_ios::copyfmt
basic_ios::fill
Diversos
Original:
Miscellaneous
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basic_ios::exceptions
basic_ios::imbue
basic_ios::rdbuf
basic_ios::tie
basic_ios::narrow
basic_ios::widen
Protegido funções de membro
Original:
Protected member functions
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basic_ios::init
basic_ios::move
basic_ios::swap
basic_ios::set_rdbuf
 
operator void*() const;
(1) (até C + 11)
explicit operator bool() const;
(2) (a partir do C++ 11)
1)
Retorna um ponteiro nulo se fail() retornos true, caso contrário, retorna um ponteiro não nulo. Esse ponteiro é implicitamente conversível para bool e pode ser usado em contexto booleano.
Original:
Returns a null pointer if fail() returns true, otherwise returns a non-null pointer. This pointer is implicitly convertible to bool and may be used in boolean context.
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2)
Retorna true se o fluxo não tem erros ocorridos e está pronto de operações de E / S. Especificamente, retorna !fail().
Original:
Returns true if the stream has no errors occurred and is ready of I/O operations. Specifically, returns !fail().
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Este operador faz com que seja possível utilizar correntes e funções que retornam referências a correntes como as condições de circuito, o que resulta na idiomática C + + entrada laços tais como while(stream >> value) {...} ou while(getline(stream, string)){...}. Tais loops executar corpo do laço apenas se a operação de entrada sucedido.
Original:
This operator makes it possible to use streams and functions that return references to streams as loop conditions, resulting in the idiomatic C++ input loops such as while(stream >> value) {...} or while(getline(stream, string)){...}. Such loops execute the loop's body only if the input operation succeeded.
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Índice

[editar] Parâmetros

(Nenhum)
Original:
(none)
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[editar] Valor de retorno

true se o fluxo não tem erros, caso contrário false.
Original:
true if the stream has no errors occurred, false otherwise.
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[editar] Exemplo

#include <iostream>
#include <sstream>
 
int main()
{
    std::istringstream s("1 2 3 error");
    int n;
    std::cout << std::boolalpha << "(bool)s is " << (bool)s << '\n';
    while (s >> n) {
        std::cout << n << '\n';
    }
    std::cout << std::boolalpha << "(bool)s is " << (bool)s << '\n';
}

Output:

(bool)s is true
1
2
3
(bool)s is false

[editar] Veja também

ios_base::iostate flags basic_ios accessors
eofbit failbit badbit good() fail() bad() eof() operator bool() operator!()
false false false true false false false true false
false false true false true true false false true
false true false false true false false false true
false true true false true true false false true
true false false false false false true true false
true false true false true true true false true
true true false false true false true false true
true true true false true true true false true