| (1) | ||
basic_string& append( size_type count, CharT ch ); | (until C++20) | |
constexpr basic_string& append( size_type count, CharT ch ); | (since C++20) | |
| (2) | ||
basic_string& append( const basic_string& str ); | (until C++20) | |
constexpr basic_string& append( const basic_string& str ); | (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) (until C++20) | |
constexpr basic_string& append( const basic_string& str,
size_type pos, size_type count = npos );
| (since C++20) | |
| (4) | ||
basic_string& append( const CharT* s, size_type count ); | (until C++20) | |
constexpr basic_string& append( const CharT* s, size_type count ); | (since C++20) | |
| (5) | ||
basic_string& append( const CharT* s ); | (until C++20) | |
constexpr basic_string& append( const CharT* s ); | (since C++20) | |
| (6) | ||
template< class InputIt > basic_string& append( InputIt first, InputIt last ); | (until C++20) | |
template< class InputIt > constexpr basic_string& append( InputIt first, InputIt last ); | (since C++20) | |
| (7) | ||
basic_string& append( std::initializer_list<CharT> ilist ); | (since C++11) (until C++20) | |
constexpr basic_string& append( std::initializer_list<CharT> ilist ); | (since C++20) | |
| (8) | ||
template< class StringViewLike > basic_string& append( const StringViewLike& t ); | (since C++17) (until C++20) | |
template< class StringViewLike > constexpr basic_string& append( const StringViewLike& t ); | (since C++20) | |
| (9) | ||
template< class StringViewLike >
basic_string& append( const StringViewLike& t,
size_type pos, size_type count = npos );
| (since C++17) (until C++20) | |
template< class StringViewLike >
constexpr basic_string& append( const StringViewLike& t,
size_type pos, size_type count = npos );
| (since C++20) |
Appends additional characters to the string.
count copies of character ch.str.[pos, pos + count) of str. count == npos, the appended substring is [pos, size()). pos > str.size(), std::out_of_range is thrown. [s, s + count). This range can contain null characters.s, as if by append(s, 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()).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.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. sv, or if count == npos, the appended subview is [pos, sv.size()). pos >= sv.size(), std::out_of_range is thrown.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.| 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 |
*this.
There are no standard complexity guarantees, typical implementations behave similar to std::vector::insert().
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).
#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
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 |
|
(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) |
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