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std::basic_ios::operator bool

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< cpp‎ | io‎ | basic ios

 
 
Entrada / salida de la biblioteca
I / O manipuladores
C-estilo I / O
Buffers
Original:
Buffers
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(obsoleto)
Arroyos
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Streams
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Abstracciones
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Abstractions
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File I / O
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File I/O
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Cadena de I / O
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String I/O
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Matriz I / O
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Array I/O
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(obsoleto)
(obsoleto)
(obsoleto)
Tipos
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Types
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Error interfaz categoría
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Error category interface
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(C++11)
 
std::basic_ios
Las funciones miembro
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Member functions
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Funciones del Estado
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State functions
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basic_ios::operator bool
Formato
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Formatting
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Varios
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Miscellaneous
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Protegido funciones miembro
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Protected member functions
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operator void*() const;
(1) (hasta C++11)
explicit operator bool() const;
(2) (desde 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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Contenido

[editar] Parámetros

(Ninguno)
Original:
(none)
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[editar] 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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[editar] 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';
}

Salida:

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

[editar] 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