std::basic_ios::operator bool

 

C++

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Utilidades de la biblioteca

Strings biblioteca

Contenedores biblioteca

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Numéricos biblioteca

Entrada / salida de la biblioteca

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Expresiones biblioteca Regular (C++11)

Operaciones de biblioteca Atómica (C++11)

Tema Biblioteca de ayuda (C++11)

 

Entrada / salida de la biblioteca

I / O manipuladores

C-estilo I / O

Buffers Original: Buffers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

basic_streambuf

basic_filebuf

basic_stringbuf

strstreambuf (obsoleto)

Arroyos Original: Streams The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Abstracciones Original: Abstractions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I / O Original: File I/O The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

basic_ifstream

basic_ofstream

basic_fstream

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basic_istringstream

basic_ostringstream

basic_stringstream

Matriz I / O Original: Array I/O The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

istrstream (obsoleto)

ostrstream (obsoleto)

strstream (obsoleto)

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streamoff

streamsize

fpos

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iostream_category (C++11)

io_errc (C++11)

 

std::basic_ios

Las funciones miembro Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

basic_ios::basic_ios

basic_ios::~basic_ios

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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

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basic_ios::copyfmt

basic_ios::fill

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basic_ios::exceptions

basic_ios::imbue

basic_ios::rdbuf

basic_ios::tie

basic_ios::narrow

basic_ios::widen

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basic_ios::init

basic_ios::move

basic_ios::swap

basic_ios::set_rdbuf

 

operator void*() const;	(1)	(hasta C + +11)
explicit operator bool() const;	(2)	(ya que C + +11)

1)

Devuelve un puntero nulo si fail() vuelve true lo contrario, devuelve un puntero no nulo. Este puntero es implícitamente convertible a bool y puede ser utilizado en el 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)

Devoluciones true si la corriente no tiene errores ocurridos y está listo de las operaciones de E / S. En concreto, devoluciones !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 hace que sea posible utilizar secuencias y funciones que devuelven referencias a corrientes como condiciones de bucle, lo que resulta en la idiomático C + + de entrada de bucles tales como while(stream >> value) {...} o while(getline(stream, string)){...}. Dichos bucles ejecutar el cuerpo del bucle sólo si la operación tuvo éxito entrada .

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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Parámetros

(Ninguno)

Original:

(none)

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Valor de retorno

true si la transferencia se no han ocurrido errores, false de otra manera .

Original:

true if the stream has no errors occurred, false otherwise.

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Ejemplo

#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

Ver también

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