std::ranges...ew::iterator(3)

std::ranges::transform_view::iterator 💅✨

okay bestie, this is a C++ Standard Libary manual page, section (3), and it's giving “niche iterator class that is actually iconic.” let’s get into it 🫶

💖 NAME 💖

std::ranges::transform_view::iterator — std::ranges::transform_view::iterator

✨ Synopsis ✨

template< bool Const >  (since C++20)
class /*iterator*/      (exposition only*)

The return type of transform_view::begin, and of transform_view::end when the underlying view is a common_range.

The type /*iterator*/<true> is returned by the const-qualified overloads. The type /*iterator*/<false> is returned by the non-const-qualified overloads.

🦋 Member types 🦋

Here’s the member-type lore, with no skipped rows 💖

• Parent (private) — const ranges::transform_view<V, F> if Const is true, otherwise ranges::transform_view<V, F>. (exposition-only member type*)
• Base (private) — const V if Const is true, otherwise V. (exposition-only member type*)
• iterator_concept — the tag depends on Base:
  • std::random_access_iterator_tag if Base models random_access_range,
  • std::bidirectional_iterator_tag if Base models bidirectional_range,
  • std::forward_iterator_tag if Base models forward_range,
  • std::input_iterator_tag otherwise.
• iterator_category — the rules are:
  • Not defined if Base does not model forward_range.
  • Otherwise, if std::invoke_result_t<F&, ranges::range_reference_t<Base>> is not a reference, std::input_iterator_tag.
  • Else, let C be std::iterator_traits<ranges::iterator_t<Base>>::iterator_category. If C is std::contiguous_iterator_tag, the type is std::random_access_iterator_tag; otherwise, the type is C.
• value_type — std::remove_cvref_t<std::invoke_result_t<F&, ranges::range_reference_t<Base>>>
• difference_type — ranges::range_difference_t<Base>

💾 Data members 💾

• current_ (private) — an iterator into (possibly const-qualified) V. (exposition-only member object*)
• parent_ (private) — a pointer to parent transform_view. (exposition-only member object*)

🎀 Member functions 🎀

• constructor (C++20) — constructs an iterator (public member function).
• base (C++20) — returns the underlying iterator (public member function).
• operator* (C++20) — accesses the transformed element (public member function).
• operator[] (C++20) — accesses an element by index (public member function).
• operator++, operator++(int), operator--, operator--(int) (C++20) — advances or decrements the underlying iterator (public member function).
• operator+=, operator-= (C++20) — listed here with no extra one-liner in the original list 🫶

🌈 Non-member functions 🌈

• operator==, operator<, operator>, operator<=, operator>=, operator<=> (C++20) — compares the underlying iterators (function).
• operator+, operator- (C++20) — performs iterator arithmetic (function).
• iter_move (C++20) — obtains an rvalue reference to the transformed element (function).

💀 Defect reports 💀

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

• P2259R1 — applied to C++20. Behavior as published: member iterator_category is always defined. Correct behavior: defined only if Base models forward_range.
• LWG 3555 — applied to C++20. Behavior as published: the definition of iterator_concept ignores const. Correct behavior: made to consider const.
• LWG 3798 — applied to C++20. Behavior as published: iterator_category is input-only if transformation result is rvalue reference. Correct behavior: may have a stronger category.

That’s the whole page, bestie 💋 — source http://cppreference.com, dated 2024.06.10, page std::ranges...ew::iterator(3). periodt 🎀