(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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