std::ranges::get(std::ranges::subrange)
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C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Ranges library
reads the value of the variant given the index or the type (if the type is unique), throws on error
(function template) [edit]
obtains a reference to real or imaginary part from a std::complex
(function template) [edit]
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++26)(C++26)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)(C++23)
(C++23)
std::ranges::subrange
get(std::ranges::subrange)
Defined in header
<ranges>
template< std::size_t N, class I, class S, ranges::subrange_kind K >
(1)
(since C++20)
requires ((N == 0 && std::copyable <I>) || N == 1)
template< std::size_t N, class I, class S, ranges::subrange_kind K >
(2)
(since C++20)
requires (N < 2)
namespace std { using ranges::get; }
(3)
(since C++20)
Provides structured binding support.
1) Obtains the iterator or sentinel from a
subrange lvalue (or a const rvalue) when N == 0 or N == 1, respectively.2) Same as (1), except that it takes a non-const
subrange rvalue.3) Overloads (1,2) are imported into namespace
std, which simplifies their usage and makes every subrange with a copyable iterator a pair-like type.[edit] Parameters
r
-
a
subrange
[edit] Return value
1,2) If N is 0, returns r.begin(). Otherwise (N is 1), returns r.end().
[edit] Example
Run this code
#include <array> #include <iostream> #include <iterator> #include <ranges> int main() { std::array a{1, -2, 3, -4}; std::ranges::subrange sub_a{std::next (a.begin()), std::prev (a.end())}; std::cout << *std::ranges::get<0>(sub_a) << ' ' // == *(begin(a) + 1) << *std::ranges::get<1>(sub_a) << '\n'; // == *(end(a) - 1) *std::get<0>(sub_a) = 42; // OK // *std::get<2>(sub_a) = 13; // Error: index can only be 0 or 1 }
Output:
-2 -4
[edit] 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 3589 | C++20 | overload (1) copies begin_ if N is 0, but I might not model copyable
|
added constraints |
[edit] See also
Structured binding (C++17)
binds the specified names to sub-objects or tuple elements of the initializer[edit]
(C++17)
(function template) [edit]
(C++26)
(function template) [edit]