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std::ranges::data(3) C++ Standard Libary 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 */; (customiza- tion 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_ref- erence_t<T>> is incomplete, then the call to ranges::data is ill-formed, no diagnos- tic required. If the argument is an lvalue or ranges::enable_bor- rowed_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 fail- ure. 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 implemen- tations. 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 con- tiguous 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) http://cppreference.com 2024.06.10 std::ranges::data(3)
NAME | Synopsis | Notes | Example | Output: | See also
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