std::basic_ostream<CharT,Traits>::operator<<
basic_ostream& operator<<( short value ); basic_ostream& operator<<( unsigned short value ); |
(1) | |
basic_ostream& operator<<( int value ); basic_ostream& operator<<( unsigned int value ); |
(2) | |
basic_ostream& operator<<( long value ); basic_ostream& operator<<( unsigned long value ); |
(3) | |
basic_ostream& operator<<( long long value ); basic_ostream& operator<<( unsigned long long value ); |
(4) | (since C++11) |
basic_ostream& operator<<( float value ); basic_ostream& operator<<( double value ); basic_ostream& operator<<( long double value ); |
(5) | |
basic_ostream& operator<<( bool value ); |
(6) | |
basic_ostream& operator<<( const void* value ); |
(7) | |
basic_ostream& operator<<( const volatile void* value ); |
(8) | (since C++23) |
basic_ostream& operator<<( std::nullptr_t ); |
(9) | (since C++17) |
basic_ostream& operator<<( std::basic_streambuf<CharT, Traits>* sb ); |
(10) | |
basic_ostream& operator<<( std::ios_base& (*func)(std::ios_base&) ); |
(11) | |
basic_ostream& operator<<( std::basic_ios<CharT,Traits>& (*func)(std::basic_ios<CharT,Traits>&) ); |
(12) | |
basic_ostream& operator<<( std::basic_ostream<CharT,Traits>& (*func)(std::basic_ostream<CharT,Traits>&) ); |
(13) |
Inserts data into the stream.
value
is
short
or
int
, then casts it to
unsigned short
or
unsigned int
if
ios_base::flags() & ios_base::basefield
is
ios_base::oct
or
ios_base::hex
. After that, casts to
long
in any case and outputs as in
(3). If
value
is
unsigned short
or
unsigned int
, casts to
unsigned long
and outputs as in
(3).
num_put::put()
. If the end of file condition was encountered during output (
put().failed() == true
), sets
ios::badbit
.
value
to
const void*
and outputs as in
(7).
*this << s
, where
s
is a null-terminated character type string.
sb
is a null pointer. If it is, executes
setstate(badbit)
and exits. Otherwise, extracts characters from the input sequence controlled by
sb
and inserts them into
*this
until one of the following conditions are met:
- end-of-file occurs on the input sequence;
- inserting in the output sequence fails (in which case the character to be inserted is not extracted);
- an exception occurs (in which case the exception is caught).
setstate(failbit)
. If an exception was thrown while extracting, sets
failbit
and, if
failbit
is set in
exceptions()
, rethrows the exception.
func(*this)
. These overloads are used to implement output I/O manipulators such as
std::endl
.
Parameters
value | - | integer, floating-point, boolean, or pointer value to insert |
func | - | function to call |
sb | - | pointer to the streambuffer to read the data from |
Return value
*this
func(*this)
Notes
There are no overloads for pointers to non-static members, pointers to volatiles, (until C++23) or function pointers (other than the ones with signatures accepted by the (11-13) overloads). Attempting to output such objects invokes implicit conversion to bool
, and, for any non-null pointer value, the value 1
is printed (unless boolalpha
was set, in which case true
is printed).
Character and character string arguments (e.g., of type char
or const char*
) are handled by the non-member overloads of operator<<
. Attempting to output a character using the member function call syntax (e.g., std::cout.operator<<('c');
) will call one of overloads (2-4) and output the numerical value. Attempting to output a character string using the member function call syntax will call overload (7) and print the pointer value instead.
Example
#include <iostream> #include <iomanip> #include <sstream> int fun() { return 42; } int main() { std::istringstream input(" \"Some text.\" "); double f = 3.14; bool b = true; std::cout << fun() // int overload << ' ' // non-member overload << std::boolalpha << b // bool overload << " " // non-member overload << std::fixed << f // double overload << input.rdbuf() // streambuf overload << fun // bool overload: there's no overload for int(*)() << std::endl; // function overload int x{}; int* p1 = &x; volatile int* p2 = &x; std::cout << "p1: " << p1 << '\n' // `const void*` overload, prints address << "p2: " << p2 << '\n'; // before C++23 (P1147): bool overload :), because // operator<<(const void*) is not a match, as it discards the `volatile` // qualifier. To fix this, C++23 adds `const volatile void*` overload, // that prints the address as expected. }
Possible output:
42 true 3.140000 "Some text." true p1: 0x7ffcea766600 p2: 0x7ffcea766600
See also
inserts character data or insert into rvalue stream (function template) |
|
performs stream input and output on strings (function template) |
|
performs stream input and output of bitsets (function template) |
|
serializes and deserializes a complex number (function template) |
|
(C++11)
|
performs stream input and output on pseudo-random number engine (function template) |
(C++11)
|
performs stream input and output on pseudo-random number distribution (function template) |
inserts a character (public member function) |
|
inserts blocks of characters (public member function) |
|
(C++17)
|
converts an integer or floating-point value to a character sequence (function) |
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