std::basic_ios::operator bool
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| operator void*() const; |
(1) | (até C++11) |
| explicit operator bool() const; |
(2) | (desde C++11) |
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.
2) 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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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'; }
Saída:
(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 |
