std::basic_string::append(3) C++ Standard Libary std::basic_string::append(3) NAME std::basic_string::append - std::basic_string::append Synopsis basic_string& append( size_type count, CharT (1) (constexpr since ch ); C++20) basic_string& append( const basic_string& str (2) (constexpr since ); C++20) basic_string& append( const basic_string& str, size_type pos, size_type (un- til C++14) count ); basic_string& append( const basic_string& str, (since C++14) size_type pos, size_type (constexpr since count = npos ); C++20) basic_string& append( const CharT* s, (4) (constexpr since size_type count ); C++20) basic_string& append( const CharT* s ); (5) (constexpr since C++20) template< class InputIt > (constexpr since basic_string& append( InputIt first, InputIt (6) C++20) last ); (3) basic_string& append( (since C++11) std::initializer_list<CharT> ilist ); (7) (constexpr since C++20) template< class StringViewLike > (since C++17) basic_string& append( const StringViewLike& t (8) (constexpr since ); C++20) template< class StringViewLike > (since C++17) basic_string& append( const StringViewLike& t, (9) (constexpr since C++20) size_type pos, size_type count = npos ); 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 con- tain 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 InputIt is an (until C++11) integral type. This overload only participates in overload resolution if InputIt (since C++11) qualifies as a LegacyInputIterator. 7) Appends characters from the initializer list ilist. 8) Implicitly converts t to a string view sv as if by std::ba- sic_string_view<CharT, Traits> sv = t;, then appends all characters from sv as if by ap- pend(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. 9) Implicitly converts t to a string view sv as if by std::ba- sic_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. 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 be- have similar to std::vector::insert(). 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). 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 Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct be- havior LWG 847 C++98 there was no exception safety added strong ex- ception safety guarantee guarantee LWG 2946 C++17 overload (8) causes ambiguity in avoided by making it a some cases template See also append_range appends a range of characters to the end (C++23) (public member function) operator+= appends characters to the end (public member function) strcat concatenates two strings (function) strncat concatenates a certain amount of characters of two strings (function) wcscat appends a copy of one wide string to another (function) appends a certain amount of wide characters from one wide string to wcsncat another (function) http://cppreference.com 2024.06.10 std::basic_string::append(3)
NAME | Synopsis | Parameters | Return value | Complexity | Exceptions | Example | Output: | See also
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