(1) | ||
template< class CharT, class Traits> basic_ostream<CharT,Traits>& operator<<( basic_ostream<CharT,Traits>& os, CharT ch ); | ||
template< class CharT, class Traits> basic_ostream<CharT,Traits>& operator<<( basic_ostream<CharT,Traits>& os, char ch ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, char ch ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, signed char ch ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, unsigned char ch ); | ||
(2) | ||
template< class CharT, class Traits > basic_ostream<CharT,Traits>& operator<<( basic_ostream<CharT,Traits>& os, const CharT* s ); | ||
template< class CharT, class Traits > basic_ostream<CharT,Traits>& operator<<( basic_ostream<CharT,Traits>& os, const char* s ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, const char* s ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, const signed char* s ); | ||
template< class Traits > basic_ostream<char,Traits>& operator<<( basic_ostream<char,Traits>& os, const unsigned char* s ); | ||
template< class CharT, class Traits, class T > basic_ostream< CharT, Traits >& operator<<( basic_ostream<CharT,Traits>&& os, const T& value ); | (3) | (since C++11) |
Inserts a character or a character string.
ch
. If the type of the character is not CharT
, it is first converted with os.widen(ch)
. Padding is determined as follows: if os.width()>1
, then os.width()-1
copies of os.fill()
are added to the output character to form the output character sequence. If (out.flags()&std::ios_base::adjustfield) == std::ios_base::left
, the fill characters are placed after the output character, otherwise before. After insertion, os.width(0)
is called to cancel the effects of std::setw
, if any.s
. CharT
matches the type of ch
), exactly traits::length(s)
characters are inserted. std::char_traits<char>::length(s)
characters are inserted. traits::length(reinterpret_cast<const char*>(s))
are inserted. Before insertion, first, all characters are widened using os.widen()
, then padding is determined as follows: if the number of characters to insert is less than os.width()
, then enough copies of os.fill()
are added to the character sequence to make its length equal os.width()
. If (out.flags()&std::ios_base::adjustfield) == std::ios_base::left
, the fill characters are added at the end of the output sequence, otherwise they are added before the output sequence. After insertion, width(0)
is called to cancel the effects of std::setw
, if any. The behavior is undefined if s
is a null pointer.
os << value
). This function template does not participate in overload resolution unless the expression os << value
is well-formed. (since C++17)
os | - | output stream to insert data to |
ch | - | reference to a character to insert |
s | - | pointer to a character string to insert |
os
.
Overload (3) in LLVM libc++ implements LWG#1203 and returns a stream of the same type as the argument, so that code such as (std::ostringstream() << 1.2).str()
compiles.
#include <iostream> #include <fstream> int main() { std::cout << "Hello, world" // the const char* overload << '\n'; // the char overload std::ofstream("test.txt") << 1.2; // rvalue overload }
Output:
Hello, world
inserts formatted data (public member function) |
|
widens characters (public member function of std::basic_ios<CharT,Traits> ) |
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