std::basic_ios::operator bool
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operator void*()const; | (1) | (avant C++11) |
explicit operator bool()const; | (2) | (depuis C++11) |
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 .
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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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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Sommaire |
[modifier]Paramètres
(Aucun)
Original:
(none)
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[modifier]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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[modifier]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
[modifier]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 |
