constexpr auto size()
    requires (ranges::sized_range<Views> && ...);
(1) (since C++23)
constexpr auto size() const
    requires (ranges::sized_range<const Views> && ...);
(2) (since C++23)

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

Equivalent to:

return std::apply(
           [](auto... sizes) {
               using CT = /*make-unsigned-like-t*/<std::common_type_t<decltype(sizes)...>>;
               return ranges::min({CT(sizes)...});
           /*tuple-transform*/(ranges::size, views_)



Return value

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


Can be tested on Compiler Explorer site.

#include <algorithm>
#include <cassert>
#include <deque>
#include <forward_list>
#include <ranges>
#include <vector>
int main()
    auto x = std::vector{1, 2, 3, 4, 5};
    auto y = std::deque{'a', 'b', 'c'};
    auto z = std::forward_list{1., 2.};
    auto v1 = std::views::zip(x, y);
    assert(v1.size() == std::min(x.size(), y.size()));
    assert(v1.size() == 3);
    [[maybe_unused]] auto v2 = std::views::zip(x, z);
//  auto sz = v2.size(); // Error, v2 does not have size():
    static_assert(not std::ranges::sized_range<decltype(z)>);

See also

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

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