std::ranges::zip_transform_view<F,Views...>:: size

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C++
Ranges library
Range adaptors
std::ranges::zip_transform_view
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zip_transform_view::size
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constexpr auto size ( )
requires ranges:: sized_range < /*InnerView*/ > ;
(1) (since C++23)
constexpr auto size ( ) const
requires ranges:: sized_range < const /*InnerView*/ >
(2) (since C++23)

Returns the number of elements in the zip_transform_view . Provided only if each underlying (adapted) range satisfies sized_range .

1,2) Equivalent to: return zip_ . size ( ) ; .

Parameters

(none)

Return value

The number of elements, which is the minimum size among all sizes of adapted view s .

Example

Run this code 
#include <algorithm>
#include <cassert>
#include <deque>
#include <forward_list>
#include <functional>
#include <iostream>
#include <ranges>
#include <vector>
 
int main()
{
    auto x = std::vector{1, 2, 3, 4, 5};
    auto y = std::deque<short>{10, 20, 30};
    auto z = std::forward_list{100., 200.};
 
    auto v1 = std::views::zip_transform(std::plus{}, x, y);
    assert(v1.size() == std::min(x.size(), y.size()));
    assert(v1.size() == 3);
    for (int i : v1)
        std::cout << i << ' ';
    std::cout << '\n';
 
    [[maybe_unused]] auto v2 = std::views::zip_transform(std::plus{}, x, z);
//  auto sz = v2.size(); // Error: z doesn't have size(), so neither does v2
    static_assert(not std::ranges::sized_range<decltype(z)>);
}

Output: 

11 22 33

See also

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