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std::basic_ios::operator bool — cppreference.com

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`operator void*() const;`	(1)	(avant C++11)
`explicit operator bool() const;`	(2)	(depuis C++11)

1)

Retourne un pointeur nul si le rendement fail() true, sinon retourne un pointeur non NULL. Ce pointeur est implicitement convertible en bool et peut être utilisé dans un contexte booléen .

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)

Retours true si le flux n'a pas eu lieu erreurs et il est prêt d'opérations d'E / S. Plus précisément, les rendements !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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Cet opérateur permet d'utiliser les flux et les fonctions qui retournent des références aux cours d'eau que les conditions de boucle, ce qui entraîne l'idiomatique C + + boucles d'entrée tels que while(stream >> value) {...} ou while(getline(stream, string)){...}. Ces boucles d'exécuter le corps de la boucle que si l'opération d'entrée réussi .

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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Paramètres

(Aucun)

Original:

(none)

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Retourne la valeur

true si le flux a aucune erreur n'est survenue, false autrement .

Original:

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

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Exemple

#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';
}

Résultat :

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

Voir aussi

`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