std::basic_ios::operator bool
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<metanoindex/>
<tbody> </tbody> operator void*() const; |
(1) | (bis C + +11) |
explicit operator bool() const; |
(2) | (seit C++11) |
1)
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 .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.The text has been machine-translated via Google Translate.
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2)
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(). The text has been machine-translated via Google Translate.
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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.The text has been machine-translated via Google Translate.
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Parameter
(None)
Original:
(none)
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Rückgabewert
true wenn der Stream hat keine Fehler aufgetreten sind, false sonst .Original:
true if the stream has no errors occurred, false otherwise.The text has been machine-translated via Google Translate.
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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
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 |