std::tuple_size<std:ranges::subrange>
From cppreference.com
| Defined in header <ranges>
|
||
template< class I, class S, ranges::subrange_kind K >
struct tuple_size<ranges::subrange<I, S, K>>
: std::integral_constant<std::size_t, 2> {};
|
(since C++20) | |
The partial specialization of std::tuple_size for std::ranges::subrange provides a compile-time way to obtain the number of components of a subrange, which is always 2, using tuple-like syntax. It is provided for structured binding support.
Inherited from std::integral_constant
Member constants
value [static] |
the constant value 2 (public static member constant) |
Member functions
operator std::size_t |
converts the object to std::size_t, returns value (public member function) |
operator() (C++14) |
returns value (public member function) |
Member types
| Type | Definition |
value_type
|
std::size_t
|
type
|
std::integral_constant<std::size_t, value>
|
Example
Run this code
#include <array>
#include <iostream>
#include <iterator>
#include <ranges>
int main()
{
static_assert(2 == std::tuple_size_v<std::ranges::subrange<int*, int*>>);
using array5 = std::array<int, 5>;
static_assert(2 == std::tuple_size<std::ranges::subrange<
array5::const_iterator, array5::const_iterator>>{});
constexpr array5 a{1, 2, 3, 4, 5};
std::ranges::subrange sub_a1{a};
for (std::cout << "sub_a1: { "; int e : sub_a1)
std::cout << e << ' ';
std::cout << "}\n";
std::ranges::subrange sub_a2{std::next(cbegin(a)), std::prev(cend(a))};
const auto [first, last] = sub_a2;
std::cout << "sub_a2 size = " << std::distance(first, last) << '\n';
for (std::cout << "sub_a2: { "; int e : sub_a2)
std::cout << e << ' ';
std::cout << "}\n";
}
Output:
sub_a1: { 1 2 3 4 5 }
sub_a2 size = 3
sub_a2: { 2 3 4 }