# std::basic_string<CharT,Traits,Allocator>::replace

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< cpp‎ | string‎ | basic string

basic_string& replace( size_type pos, size_type count, const basic_string& str ); | (1) | (constexpr since C++20)
basic_string& replace( const_iterator first, const_iterator last, const basic_string& str ); | (2) | (constexpr since C++20)
| (3) |
basic_string& replace( size_type pos, size_type count, const basic_string& str, size_type pos2, size_type count2 ); |  | (until C++14)
basic_string& replace( size_type pos, size_type count, const basic_string& str, size_type pos2, size_type count2 = npos ); |  | (since C++14) (constexpr since C++20)
basic_string& replace( size_type pos, size_type count, const CharT* cstr, size_type count2 ); | (4) | (constexpr since C++20)
basic_string& replace( const_iterator first, const_iterator last, const CharT* cstr, size_type count2 ); | (5) | (constexpr since C++20)
basic_string& replace( size_type pos, size_type count, const CharT* cstr ); | (6) | (constexpr since C++20)
basic_string& replace( const_iterator first, const_iterator last, const CharT* cstr ); | (7) | (constexpr since C++20)
basic_string& replace( size_type pos, size_type count, size_type count2, CharT ch ); | (8) | (constexpr since C++20)
basic_string& replace( const_iterator first, const_iterator last, size_type count2, CharT ch ); | (9) | (constexpr since C++20)
template< class InputIt > basic_string& replace( const_iterator first, const_iterator last, InputIt first2, InputIt last2 ); | (10) | (constexpr since C++20)
basic_string& replace( const_iterator first, const_iterator last, std::initializer_list <CharT> ilist ); | (11) | (since C++11) (constexpr since C++20)
template< class StringViewLike > basic_string& replace( size_type pos, size_type count, const StringViewLike& t ); | (12) | (since C++17) (constexpr since C++20)
template< class StringViewLike > basic_string& replace( const_iterator first, const_iterator last, const StringViewLike& t ); | (13) | (since C++17) (constexpr since C++20)
template< class StringViewLike > basic_string& replace( size_type pos, size_type count, const StringViewLike& t, size_type pos2, size_type count2 = npos ); | (14) | (since C++17) (constexpr since C++20)

Replaces the characters in the range `[`begin() + pos`,` begin() + std::min (pos + count, size())`)` or `[`first`,` last`)` with given characters.

1,2) Those characters are replaced with str.
3) Those characters are replaced with a substring `[`pos2`,` std::min (pos2 + count2, str.size())`)` of str.
4,5) Those characters are replaced with the characters in the range `[`cstr`,` cstr + count2`)`.
If `[`cstr`,` cstr + count2`)` is not a valid range, the behavior is undefined.
6,7) Those characters are replaced with the characters in the range `[`cstr`,` cstr + Traits::length(cstr)`)`.
8,9) Those characters are replaced with count2 copies of ch.
10) Those characters are replaced with the characters in the range `[`first2`,` last2`)` as if by replace(first, last, basic_string(first2, last2, get_allocator())).
11) Those characters are replaced with the characters in ilist.
12,13) Implicitly converts t to a string view sv as if by std::basic_string_view <CharT, Traits> sv = t;, then those characters are replaced with the characters from sv.
These overloads participate 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.
14) Implicitly converts t to a string view sv as if by std::basic_string_view <CharT, Traits> sv = t;, then those characters are replaced with the characters from the subview sv.substr(pos2, count2).
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 `[`begin()`,` first`)` or `[`first`,` last`)` is not a valid range, the behavior is undefined.

### Parameters

pos | - | start of the substring that is going to be replaced
count | - | length of the substring that is going to be replaced
first, last | - | range of characters that is going to be replaced
str | - | string to use for replacement
pos2 | - | start of the substring to replace with
count2 | - | number of characters to replace with
cstr | - | pointer to the character string to use for replacement
ch | - | character value to use for replacement
first2, last2 | - | range of characters to use for replacement
ilist | - | initializer list with the characters to use for replacement
t | - | object (convertible to std::basic_string_view) with the characters to use for replacement
Type requirements
- `InputIt` must meet the requirements of LegacyInputIterator.

### Return value

*this.

### Exceptions

1) Throws std::out_of_range if pos > size().
3) Throws std::out_of_range if pos > size() or pos2 > str.size().
4,6,8) Throws std::out_of_range if pos > size().
12,14) Throws std::out_of_range if pos > size().

If the operation would cause `size()` to exceed `max_size()`, throws std::length_error.

If an exception is thrown for any reason, these functions have no effect (strong exception safety guarantee).

### Example

| This section is incomplete Reason: no example

### 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 847 | C++98 | there was no exception safety guarantee | added strong exception safety guarantee
LWG 1323 | C++98 | the types of first and last were `iterator` | changed to `const_iterator`
LWG 2946 | C++17 | overloads (12,13) caused ambiguity in some cases | avoided by making them templates

### See also

replace_with_range (C++23) | replaces specified portion of a string with a range of characters (public member function)
regex_replace (C++11) | replaces occurrences of a regular expression with formatted replacement text (function template)
replacereplace_if | replaces all values satisfying specific criteria with another value (function template)

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