std::basic_string<CharT,Traits,Allocator>::append
basic_string& append( size_type count, CharT ch ); |
(1) | |
basic_string& append( const basic_string& str ); |
(2) | |
(3) | ||
basic_string& append( const basic_string& str, size_type pos, |
(until C++14) | |
basic_string& append( const basic_string& str, size_type pos, |
(since C++14) | |
basic_string& append( const CharT* s, size_type count ); |
(4) | |
basic_string& append( const CharT* s ); |
(5) | |
template< class InputIt > basic_string& append( InputIt first, InputIt last ); |
(6) | |
basic_string& append( std::initializer_list<CharT> ilist ); |
(7) | (since C++11) |
template < class T > basic_string& append( const T& t ); |
(8) | (since C++17) |
template < class T > basic_string& append( const T& t, size_type pos, |
(9) | (since C++17) |
Appends additional characters to the string.
count
copies of character ch
str
[pos, pos+count)
of str
. If the requested substring lasts past the end of the string, or if count == npos, the appended substring is [pos, size())
. If pos > str.size(), std::out_of_range is thrown. [s, s + count)
. This range can contain null characters.s
. The length of the string is determined by the first null character using Traits::length(s). [first, last)
.
This overload has the same effect as overload (1) if |
(until C++11) |
This overload only participates in overload resolution if |
(since C++11) |
ilist
.t
to a string view sv
as if by std::basic_string_view<CharT, Traits> sv = t;, then appends all characters from sv
as if by append(sv.data(), sv.size()). This overload only participates in overload resolution if std::is_convertible_v<const T&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const T&, const CharT*> is false.t
to a string view sv
as if by std::basic_string_view<CharT, Traits> sv = t;, then appends the characters from the subview [pos, pos+count)
of sv
. If the requested subview extends past the end of sv
, or if count == npos, the appended subview is [pos, sv.size())
. If pos >= sv.size(), std::out_of_range is thrown. This overload only participates in overload resolution if std::is_convertible_v<const T&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const T&, const CharT*> is false.Parameters
count | - | number of characters to append |
pos | - | the index of the first character to append |
ch | - | character value to append |
first, last | - | range of characters to append |
str | - | string to append |
s | - | pointer to the character string to append |
ilist | - | initializer list with the characters to append |
t | - | object convertible to std::basic_string_view with the characters to append |
Return value
*this
Complexity
There are no standard complexity guarantees, typical implementations behave similar to std::vector::insert.
Exceptions
If an exception is thrown for any reason, this function has no effect (strong exception guarantee). (since C++11)
If the operation would result in size() > max_size()
, throws std::length_error.
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2946 | C++17 | string_view overload causes ambiguity in some cases
|
avoided by making it a template |
Example
#include <string> #include <iostream> int main() { std::basic_string<char> str = "string"; const char* cptr = "C-string"; const char carr[] = "Two and one"; std::string output; // 1) Append a char 3 times. // Notice, this is the only overload accepting chars. output.append(3, '*'); std::cout << "1) " << output << "\n"; // 2) Append a whole string output.append(str); std::cout << "2) " << output << "\n"; // 3) Append part of a string (last 3 letters, in this case) output.append(str, 3, 3); std::cout << "3) " << output << "\n"; // 4) Append part of a C-string // Notice, because `append` returns *this, we can chain calls together output.append(1, ' ').append(carr, 4); std::cout << "4) " << output << "\n"; // 5) Append a whole C-string output.append(cptr); std::cout << "5) " << output << "\n"; // 6) Append range output.append(&carr[3], std::end(carr)); std::cout << "6) " << output << "\n"; // 7) Append initializer list output.append({ ' ', 'l', 'i', 's', 't' }); std::cout << "7) " << output << "\n"; }
Output:
1) *** 2) ***string 3) ***stringing 4) ***stringing Two 5) ***stringing Two C-string 6) ***stringing Two C-string and one 7) ***stringing Two C-string and one list
See also
appends characters to the end (public member function) | |
concatenates two strings (function) | |
concatenates a certain amount of characters of two strings (function) | |
appends a copy of one wide string to another (function) | |
appends a certain amount of wide characters from one wide string to another (function) |