std::basic_string<CharT,Traits,Allocator>::append
From cppreference.com
< cpp | string | basic string
basic_string& append( size_type count, CharT ch ); |
(1) | (constexpr since C++20) |
basic_string& append( const basic_string& str ); |
(2) | (constexpr since C++20) |
(3) | ||
basic_string& append( const basic_string& str, size_type pos, size_type count ); |
(until C++14) | |
basic_string& append( const basic_string& str, size_type pos, size_type count = npos ); |
(since C++14) (constexpr since C++20) |
|
basic_string& append( const CharT* s, size_type count ); |
(4) | (constexpr since C++20) |
basic_string& append( const CharT* s ); |
(5) | (constexpr since C++20) |
template< class InputIt > basic_string& append( InputIt first, InputIt last ); |
(6) | (constexpr since C++20) |
basic_string& append( std::initializer_list<CharT> ilist ); |
(7) | (since C++11) (constexpr since C++20) |
template< class StringViewLike > basic_string& append( const StringViewLike& t ); |
(8) | (since C++17) (constexpr since C++20) |
template< class StringViewLike > basic_string& append( const StringViewLike& t, |
(9) | (since C++17) (constexpr since C++20) |
Appends additional characters to the string.
1) Appends count copies of character ch.
2) Appends string str.
3) Appends a substring
[
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.
4) Appends characters in the range
[
s,
s + count)
. This range can contain null characters. If
[
s,
s + count)
is not a valid range, the behavior is undefined.5) Appends the null-terminated character string pointed to by s, as if by append(s, Traits::length(s)).
6) Appends characters in the range
[
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) |
7) Appends characters from the initializer list ilist.
8) Implicitly converts 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 participates in overload resolution only if std::is_convertible_v<const StringViewLike&,
std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.
std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.
9) Implicitly converts 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 participates in overload resolution only if std::is_convertible_v<const StringViewLike&,
std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.
std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.
Contents |
[edit] 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 |
[edit] Return value
*this
[edit] Complexity
There are no standard complexity guarantees, typical implementations behave similar to std::vector::insert().
[edit] Exceptions
If the operation would result in size
() >
max_size
(), throws std::length_error.
If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).
[edit] Example
Run this code
#include <iostream> #include <string> 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
[edit] 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 847 | C++98 | there was no exception safety guarantee | added strong exception safety guarantee |
LWG 2946 | C++17 | overload (8) causes ambiguity in some cases | avoided by making it a template |
[edit] See also
(C++23) |
appends a range of characters to the end (public member function) |
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) |