std::basic_string::insert(3)

std::basic_string::insert(3) 🌸

okay bestie, this is the std::basic_string::insert(3) page from the C++ Standard Libary (their spelling, not mine 😭💀). It's giving “string surgery, but make it C++,” and honestly? iconic. You're literally inserting characters into an existing string at an index or before an iterator. No cap.

🎀 NAME 🎀

std::basic_string::insert — std::basic_string::insert

✨ Synopsis ✨

basic_string& insert(size_type index, size_type count, CharT ch);                 // (1) constexpr since C++20
basic_string& insert(size_type index, const CharT* s);                            // (2) constexpr since C++20
basic_string& insert(size_type index, const CharT* s, size_type count);           // (3) constexpr since C++20
basic_string& insert(size_type index, const basic_string& str);                   // (4) constexpr since C++20

basic_string& insert(size_type index, const basic_string& str,
                     size_type s_index, size_type count);                         // (5) until C++14
basic_string& insert(size_type index, const basic_string& str,
                     size_type s_index, size_type count = npos);                  // (5) since C++14; constexpr since C++20

iterator insert(iterator pos, CharT ch);                                         // (6) until C++11
iterator insert(const_iterator pos, CharT ch);                                   // (6) since C++11; constexpr since C++20

void insert(iterator pos, size_type count, CharT ch);                            // (7) until C++11
iterator insert(const_iterator pos, size_type count, CharT ch);                  // (7) since C++11; constexpr since C++20

template<class InputIt>
void insert(iterator pos, InputIt first, InputIt last);                          // (8) until C++11
template<class InputIt>
iterator insert(const_iterator pos, InputIt first, InputIt last);                // (8) since C++11; constexpr since C++20

iterator insert(const_iterator pos, std::initializer_list<CharT> ilist);          // (9) since C++11; constexpr since C++20

template<class StringViewLike>
basic_string& insert(size_type index, const StringViewLike& t);                  // (10) since C++17; constexpr since C++20

template<class StringViewLike>
basic_string& insert(size_type index, const StringViewLike& t,
                     size_type t_index, size_type count = npos);                 // (11) since C++17; constexpr since C++20

Inserts characters into the string. Yeah, that's the whole vibe: characters go in, string gets longer, we celebrate 🎉

1. (1) Inserts count copies of character ch at the position index.
2. (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. (3) Inserts the characters in the range [s, s + count) at the position index. The range can contain null characters.
4. (4) Inserts string str at the position index.
5. (5) Inserts a string, obtained by str.substr(s_index, count) at the position index.
6. (6) Inserts character ch before the character pointed by pos.
7. (7) Inserts count copies of character ch before the element (if any) pointed by pos.
8. (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. (9) Inserts elements from initializer list ilist before the element (if any) pointed by pos.
10. (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. (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. bestie, respect the iterator or face the consequences 💀

🦋 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 exception, it is rethrown. (since C++20)

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee). yes bestie, it said strong exception safety guarantee — we love a function that doesn't leave you in a messy situation 🫶

🌈 Example 🌈

#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.

• LWG 7 — Applied to C++98: overload (8) referred to a non-existing overload; correct behavior: refers to overload (4) correctly.
• LWG 847 — Applied to C++98: there was no exception safety guarantee; correct behavior: added strong exception safety guarantee.
• LWG 2946 — Applied to C++17: overload (10) caused ambiguity in some cases; correct behavior: avoided by making it a 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)

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mwah 💋 this page is served fresh from http://cppreference.com, version/date 2024.06.10 — now go slay those insertions, bestie 🫶✨