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

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C++
Ranges library
Range adaptors
std::ranges::transform_view
Member functions
Deduction guides
Iterator
transform_view:: iterator ::base
Sentinel
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

Run this code 
#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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