std::ranges::enumerate_view<V>::size
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std::ranges::enumerate_view
enumerate_view::size
(C++26)
constexpr auto size() requires ranges::sized_range <V>;
(1)
(since C++23)
constexpr auto size() const requires ranges::sized_range <const V>;
(2)
(since C++23)
Returns the number of elements. Equivalent to return ranges::size (base_);, where base_ is the underlying view.
Contents
[edit] Parameters
(none)
[edit] Return value
The number of elements.
[edit] Example
Run this code
#include <cassert> #include <forward_list> #include <ranges> #include <string_view> int main() { constexpr static auto v1 = {1, 2, 3, 4, 5}; constexpr auto ev1{v1 | std::views::enumerate}; static_assert(ev1.size() == 5); static_assert(std::ranges::sized_range <decltype(v1)>); auto v2 = std::forward_list {1, 2, 3, 4, 5}; auto ev2 {v2 | std::views::enumerate}; static_assert(not std::ranges::sized_range <decltype(v2)>); // auto size = ev2.size(); // Error: v2 is not a sized range assert (std::ranges::distance (v2) == 5); // OK, distance does not require sized // range, but has O(N) complexity here }