= `string`

Modifiable sequences of characters are represented using objects of type <<ref_string>>.

The interface and functionality of <<ref_string>> is the same as {std_string} except that:

<<ref_string>> is not a class template,

<<ref_string>> uses `char` as its character type,

redundant overloads for string operations have been replaced

with a <<ref_string_view>>-based interface,

access to characters in the range `[size(), capacity())` is permitted,

<<ref_storage_ptr>> is used instead of {req_Allocator}, and

small buffer optimisation is guaranteed, which avoids allocating memory for

small strings.

With augmented interface, operations requiring an input string are implemented as a single overload with a parameter of type <<ref_string_view>>, and can accept most string-like objects. Objects such as null terminated character pointers, `std::string`, <<ref_string>>, subranges of strings, and objects convertible to <<ref_string_view>> can all be passed to these functions.

More formally, `std::string` member function overloads that accept any of the following parameter combinations as an input string:

a `std::string` parameter, or

a `std::string` parameter and two `size_type` parameters that specify a

substring, or

a parameter of a type convertible to <<ref_string_view>>, or

a parameter of a type convertible to <<ref_string_view>> and two

`size_type` parameters that specify a substring, or

a `const_pointer` parameter, or