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

Since C++20

Returns the number of elements.

# Declarations

constexpr auto size() requires ranges::sized_range<V>;

(since C++20)

constexpr auto size() const requires ranges::sized_range<const V>;

(since C++20)

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

# See also