std::basic_string<CharT,Traits,Allocator>::append (3) - Linux Manuals

std::basic_string<CharT,Traits,Allocator>::append: std::basic_string<CharT,Traits,Allocator>::append

NAME

std::basic_string<CharT,Traits,Allocator>::append - std::basic_string<CharT,Traits,Allocator>::append

Synopsis

basic_string& append( size_type count, CharT ch ); (1)
basic_string& append( const basic_string& str ); (2)
basic_string& append( const basic_string& str,
size_type pos, (until C++14)
size_type count );
basic_string& append( const basic_string& str,
size_type pos, (since C++14)
size_type count = npos );
basic_string& append( const CharT* s, size_type count ); (4)
basic_string& append( const CharT* s ); (3) (5)
template< class InputIt > (6)
basic_string& append( InputIt first, InputIt last );
basic_string& append( std::initializer_list<CharT> ilist ); (7) (since C++11)
template < class T > (8) (since C++17)
basic_string& append( const T& t );
template < class T >
basic_string& append( const T& t, size_type pos, (9) (since C++17)
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 contain null characters.
5) Appends the null-terminated character string pointed to by s. The length of the string is determined by the first null character using Traits::length(s).
6) Appends characters in the range [first, last).

This overload has the same effect as overload (1) if InputIt is an integral type. (until C++11)
This overload only participates in overload resolution if InputIt qualifies as an LegacyInputIterator (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 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.
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 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

// Run this code

  #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