std::basic_string::insert(3)

NAME
std::basic_string::insert - std::basic_string::insert

Synopsis
   basic_string& insert( (constexpr
   size_type index, size_type (1) since
   count, CharT ch ); C++20)
   basic_string& insert( (constexpr
   size_type index, const (2) since
   CharT* s ); C++20)
   basic_string& insert( (constexpr
   size_type index, const (3) since
   CharT* s, size_type count ); C++20)
   basic_string& insert( (constexpr
   size_type index, const (4) since
   basic_string& str ); C++20)
   basic_string& insert(
   size_type index, const
   basic_string& str, (until
                        C++14)
   size_type s_index, size_type
   count );
   basic_string& insert( (since
   size_type index, const C++14)
   basic_string& str, (constexpr
                        since
   size_type s_index, size_type C++20)
   count = npos );
   iterator insert( iterator (until
   pos, CharT ch ); C++11)
                        (since
   iterator insert( C++11)
   const_iterator pos, CharT ch (constexpr
   ); since
                        C++20)
   void insert( iterator pos, (until
   size_type count, CharT ch ); C++11)
                        (since
   iterator insert( C++11)
   const_iterator pos, (constexpr
   size_type count, CharT ch ); since
                        C++20)
   template< class InputIt >
   void insert( iterator pos, (5) (until
   InputIt first, InputIt last C++11)
   );
   template< class InputIt > (since
   iterator insert( C++11)
   const_iterator pos, InputIt (constexpr
   first, InputIt last ); (6) since
                        C++20)
   iterator insert( (since
   const_iterator pos, (7) C++11)
   std::initializer_list<CharT> (9) (constexpr
   ilist ); since
                        C++20)
   template< class (8) (since
   StringViewLike > C++17)
   basic_string& insert( (10) (constexpr
   size_type index, const since
   StringViewLike& t ); C++20)
   template< class
   StringViewLike >
                        (since
   basic_string& insert( C++17)
   size_type index, const (11) (constexpr
   StringViewLike& t, since
                        C++20)
   size_type t_index, size_type
   count = npos );
   Inserts characters into the string.
   1) Inserts count copies of character ch at the position index.
   2) Inserts null-terminated character string pointed to by s at the position index.
   The length of the string is determined by the first null character using
   Traits::length(s).
   3) Inserts the characters in the range [s, s + count) at the position index. The
   range can contain null characters.
   4) Inserts string str at the position index.
   5) Inserts a string, obtained by str.substr(s_index, count) at the position index.
   6) Inserts character ch before the character pointed by pos.
   7) Inserts count copies of character ch before the element (if any) pointed by pos.
   8) Inserts characters from the range [first, last) before the element (if any)
   pointed by pos, as if by insert(pos - begin(), basic_string(first, last,
   get_allocator())).
   This overload does not participate in overload resolution if InputIt (since C++11)
   does not satisfy LegacyInputIterator.
   9) Inserts elements from initializer list ilist before the element (if any) pointed
   by pos.
   10) Implicitly converts t to a string view sv as if by std::basic_string_view<CharT,
   Traits> sv = t;, then inserts the elements from sv before the element (if any)
   pointed by index, as if by insert(index, 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.
   11) Implicitly converts t to a string view sv as if by std::basic_string_view<CharT,
   Traits> sv = t;, then inserts, before the element (if any) pointed by index, the
   characters from the subview [t_index, t_index + count) of sv.
     * If the requested subview lasts past the end of sv, or if count == npos, the
       resulting subview is [t_index, sv.size()).
     * If t_index > sv.size(), or if index > 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.
   If pos is not a valid iterator on *this, the behavior is undefined.

Parameters
   index - position at which the content will be inserted
   pos - iterator before which the characters will be inserted
   ch - character to insert
   count - number of characters to insert
   s - pointer to the character string to insert
   str - string to insert
   first, last - range defining characters to insert
   s_index - position of the first character in str to insert
   ilist - std::initializer_list to insert the characters from
   t - object (convertible to std::basic_string_view) to insert the
                 characters from
   t_index - position of the first character in t to insert

Type requirements
   -
   InputIt must meet the requirements of LegacyInputIterator.

Return value
   1-5) *this
   6-9) An iterator which refers to the copy of the first inserted character or pos if
   no characters were inserted (count == 0 or first == last or ilist.size() == 0)
   10,11) *this

Exceptions
   1-4,10) Throws std::out_of_range if index > size().
   5) Throws std::out_of_range if index > size() or if s_index > str.size().
   11) Throws std::out_of_range if index > size() or if t_index > sv.size().
   In all cases, throws std::length_error if size() + ins_count > max_size() where
   ins_count is the number of characters that will be inserted.
   In all cases, if std::allocator_traits<Allocator>::allocate throws an (since C++20)
   exception, it is rethrown.
   If an exception is thrown for any reason, this function has no effect (strong
   exception safety guarantee).

Example
// Run this code
 #include <cassert>
 #include <iterator>
 #include <string>
 using namespace std::string_literals;
 int main()
 {
     std::string s = "xmplr";
     // insert(size_type index, size_type count, char ch)
     s.insert(0, 1, 'E');
     assert("Exmplr" == s);
     // insert(size_type index, const char* s)
     s.insert(2, "e");
     assert("Exemplr" == s);
     // insert(size_type index, string const& str)
     s.insert(6, "a"s);
     assert("Exemplar" == s);
     // insert(size_type index, string const& str,
     // size_type s_index, size_type count)
     s.insert(8, " is an example string."s, 0, 14);
     assert("Exemplar is an example" == s);
     // insert(const_iterator pos, char ch)
     s.insert(s.cbegin() + s.find_first_of('n') + 1, ':');
     assert("Exemplar is an: example" == s);
     // insert(const_iterator pos, size_type count, char ch)
     s.insert(s.cbegin() + s.find_first_of(':') + 1, 2, '=');
     assert("Exemplar is an:== example" == s);
     // insert(const_iterator pos, InputIt first, InputIt last)
     {
         std::string seq = " string";
         s.insert(s.begin() + s.find_last_of('e') + 1,
             std::begin(seq), std::end(seq));
         assert("Exemplar is an:== example string" == s);
     }
     // insert(const_iterator pos, std::initializer_list<char>)
     s.insert(s.cbegin() + s.find_first_of('g') + 1, {'.'});
     assert("Exemplar is an:== example string." == s);
 }
   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 7 C++98 overload (8) referred to a non-existing refers to overload (4)
                       overload correctly
   LWG 847 C++98 there was no exception safety guarantee added strong exception
                        safety guarantee
   LWG 2946 C++17 overload (10) caused ambiguity in some avoided by making it a
                       cases template

See also
   insert_range inserts a range of characters
   (C++23) (public member function)
   append appends characters to the end
                (public member function)
   push_back appends a character to the end
                (public member function)