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)