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std::ranges::transform_view<V,F>::iterator<Const>::base

constexpr const ranges::iterator_t<Base>& base() const & noexcept;	(1)	(since C++20)
constexpr ranges::iterator_t<Base> base() &&;	(2)	(since C++20)

Returns the underlying iterator.

1) Returns a reference to the underlying iterator.

2) Move constructs the result from the underlying iterator.

Parameters

(none).

Return value

1) A reference to the underlying iterator.

2) An iterator move constructed from the underlying iterator.

Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <ranges>
 
int main()
{
    const auto v = { 0, 1, 2, 3, 4 };
    auto x2 = [](int x) { return x << 1; };
    std::ranges::transform_view tv{ v, x2 };
    std::ostream_iterator<int> ostr{ std::cout, " " };
 
    std::ranges::copy(v, ostr), std::cout << '\n';
    std::ranges::copy(tv.base(), ostr), std::cout << '\n';
    std::ranges::copy(tv, ostr), std::cout << '\n';
}

Output:

0 1 2 3 4
0 1 2 3 4
0 2 4 6 8

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3533	C++20	the `const&` overload of `base` returns a copy of the underlying iterator	returns a reference
LWG 3593	C++20	the `const&` overload of `base` might not be noexcept	made noexcept

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