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std::ranges::transform_view<V,F>::size

constexpr auto size() requires ranges::sized_range<V>;
 (since C++20) 
constexpr auto size() const requires ranges::sized_range<const V>;
 (since C++20)

Returns the number of elements.

Returns ranges::size(base_), where base_ is the underlying view.

Parameters

(none).

Return value

The number of elements.

Notes

If V does not model forward_range, size() might not be well-defined after a call to begin().

Example

#include <iostream>
#include <ranges>
#include <string>
#include <cctype>
 
int main()
{
    std::string s{"The length of this string is 42 characters"};
    auto tv = std::ranges::transform_view{s, [](char c) -> char {
        return std::toupper(c); }
    };
    for (auto x: tv) { std::cout << x; };
    std::cout << "\nsize = " << tv.size() << '\n';
}

Output:

THE LENGTH OF THIS STRING IS 42 CHARACTERS
size = 42

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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