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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