std::basic_ios::operator bool
De cppreference.com
<metanoindex/>
<tbody> </tbody> operator void*() const; |
(1) | (até C++11) |
explicit operator bool() const; |
(2) | (desde 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.The text has been machine-translated via Google Translate.
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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(). The text has been machine-translated via Google Translate.
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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.The text has been machine-translated via Google Translate.
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Parâmetros
(Nenhum)
Original:
(none)
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Valor de retorno
true se o fluxo não tem erros, caso contrário false.Original:
true if the stream has no errors occurred, false otherwise.The text has been machine-translated via Google Translate.
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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';
}
Saída:
(bool)s is true
1
2
3
(bool)s is false