NAME¶

std::ranges::enumerate_view::size - std::ranges::enumerate_view::size

Synopsis¶

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.

Parameters¶

(none)

Return value¶

The number of elements.

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
}

See also¶

ranges::size returns an integer equal to the size of a range
(C++20) (customization point object)
ranges::ssize returns a signed integer equal to the size of a range
(C++20) (customization point object)