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Varianti

std::basic_ios::operator bool

Da cppreference.com.
< cpp‎ | io‎ | basic ios

 
 
Ingresso / libreria di output
I / O manipolatori
C-style I / O
Buffer
Original:
Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf(deprecato)
Streams
Original:
Streams
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Astrazioni
Original:
Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I / O
Original:
File I/O
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basic_ifstream
basic_ofstream
basic_fstream
String I / O
Original:
String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
Array I / O
Original:
Array I/O
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istrstream(deprecato)
ostrstream(deprecato)
strstream(deprecato)
Tipi
Original:
Types
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streamoff
streamsize
fpos
Errore categoria interfaccia
Original:
Error category interface
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iostream_category(C++11)
io_errc(C++11)
 
std::basic_ios
Membri funzioni
Original:
Member functions
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basic_ios::basic_ios
basic_ios::~basic_ios
Le funzioni dello Stato
Original:
State functions
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basic_ios::good
basic_ios::eof
basic_ios::fail
basic_ios::bad
basic_ios::operator!
basic_ios::operator bool
basic_ios::rdstate
basic_ios::setstate
basic_ios::clear
Formattazione
Original:
Formatting
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basic_ios::copyfmt
basic_ios::fill
Varie
Original:
Miscellaneous
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basic_ios::exceptions
basic_ios::imbue
basic_ios::rdbuf
basic_ios::tie
basic_ios::narrow
basic_ios::widen
Protetto funzioni membro
Original:
Protected member functions
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basic_ios::init
basic_ios::move
basic_ios::swap
basic_ios::set_rdbuf
 
operator void*() const;
(1) (C fino + 11)
explicit operator bool() const;
(2) (dal C++11)
1)
Restituisce un puntatore nullo se fail() ritorna true, altrimenti restituisce un valore non null pointer. Questo puntatore è convertibile in modo implicito bool e può essere utilizzato in un contesto 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)
Restituisce true se il flusso non ci sono errori commessi ed è pronto di operazioni di I / O. In particolare, torna !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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Questo operatore permette di utilizzare i flussi e funzioni che restituiscono riferimenti a flussi come condizioni di ciclo, con conseguente idiomatica C + + ingresso cicli come while(stream >> value) {...} o while(getline(stream, string)){...}. Tali cicli di eseguire il corpo del ciclo solo se l'operazione è riuscita ingresso.
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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Indice

[modifica] Parametri

(Nessuno)
Original:
(none)
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[modifica] Valore di ritorno

true se il flusso è non si sono verificati errori, false altrimenti.
Original:
true if the stream has no errors occurred, false otherwise.
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[modifica] Esempio

#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

[modifica] Vedi anche

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