std::basic_ios::operator bool
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| operator void*() const; |
(1) | (bis C + +11) |
| explicit operator bool() const; |
(2) | (seit C++11) |
Gibt eine Null-Zeiger, wenn fail() kehrt true, sonst gibt einen Nicht-Null-Zeiger. Dieser Zeiger ist implizit konvertierbar bool und kann in Booleschen Kontext verwendet werden .
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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true kehrt, wenn der Stream hat keine Fehler aufgetreten sind und ist bereit von I / O-Operationen. Insbesondere kehrt !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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Dieser Operator ermöglicht es, Ströme und Funktionen, die Verweise zurück auf Streams als Loop Bedingungen, was in der idiomatischen C + + verwenden Input-Schleifen, wie while(stream >> value) {...} oder while(getline(stream, string)){...}. Solche Schleifen führen der Schleife Körper nur, wenn die Eingabe-Operation gelungen .
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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Inhaltsverzeichnis |
[Bearbeiten] Parameter
(None)
Original:
(none)
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[Bearbeiten] Rückgabewert
true wenn der Stream hat keine Fehler aufgetreten sind, false sonst .
Original:
true if the stream has no errors occurred, false otherwise.
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[Bearbeiten] Beispiel
#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
[Bearbeiten] Siehe auch
| 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 |
