std::ranges::data(3)

NAME
std::ranges::data - std::ranges::data

Synopsis
   Defined in header <ranges>
   Defined in header <iterator>
   inline namespace /* unspecified */ {
       inline constexpr /* unspecified */ data = /* (since C++20)
   unspecified */; (customization point object)
   }
   Call signature
   template< class T >
       requires /* see below */ (since C++20)
   constexpr std::remove_reference_t<
       ranges::range_reference_t<T>>* data( T&& t );
   Returns a pointer to the first element of a contiguous range.
   If T is an array type and std::remove_all_extents_t<std::remove_reference_t<T>> is
   incomplete, then the call to ranges::data is ill-formed, no diagnostic required.
   If the argument is an lvalue or ranges::enable_borrowed_range<std::remove_cv_t<T>>
   is true, a call to ranges::data is expression-equivalent to:
    1. decay-copy(t.data())
       (until C++23)
       auto(t.data())
       (since C++23), if that expression is valid and its type is a pointer to an
       object type.
    2. Otherwise, std::to_address(ranges::begin(t)), if the expression ranges::begin(t)
       is valid and its type models std::contiguous_iterator.
   In all other cases, a call to ranges::data is ill-formed, which can result in
   substitution failure when ranges::data(e) appears in the immediate context of a
   template instantiation.

Notes
   If the argument is an rvalue (i.e. T is an object type) and
   ranges::enable_borrowed_range<std::remove_cv_t<T>> is false, the call to
   ranges::data is ill-formed, which also results in substitution failure.
   If ranges::data(e) is valid for an expression e, then it returns a pointer to an
   object.
   The C++20 standard requires that if the underlying data function call returns a
   prvalue, the return value is move-constructed from the materialized temporary
   object. All implementations directly return the prvalue instead. The requirement is
   corrected by the post-C++20 proposal P0849R8 to match the implementations.

Example
// Run this code
 #include <cstring>
 #include <iostream>
 #include <ranges>
 #include <string>
 int main()
 {
     std::string s{"Hello world!\n"};
     char a[20]; // storage for a C-style string
     std::strcpy(a, std::ranges::data(s));
     // [data(s), data(s) + size(s)] is guaranteed to be an NTBS
     std::cout << a;
 }

Output:
 Hello world!

See also
   ranges::cdata obtains a pointer to the beginning of a read-only contiguous range
   (C++20) (customization point object)
   ranges::begin returns an iterator to the beginning of a range
   (C++20) (customization point object)
   data obtains the pointer to the underlying array
   (C++17) (function template)