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Section: 24.3.9.5 [forward.list.modifiers] Status: WP Submitter: Tomasz Kamiński Opened: 2022-11-08 Last modified: 2022-11-17
Priority: Not Prioritized
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Discussion:
This is resolution of GB-101 (24.3.9.5 [forward.list.modifiers] p12,15,20,21 Missing preconditions on forward_list modifiers).
Some of the modifiers to forward_list are special to that container and accordingly are not described in 24.2 [container.requirements]. Specifically, insert_after (iterator overload), insert_range_after and emplace_after do not verify that the value_type is Cpp17EmplaceConstructible from the appropriate argument(s). Furthermore insert_after (value overloads) are missing Cpp17CopyInsertable/Cpp17MoveInsertable requirements.
[Kona 2022-11-08; Move to Ready]
[Kona 2022-11-12; Correct status to Immediate]
[2022-11-12 Approved at November 2022 meeting in Kona. Status changed: Immediate → WP.]
Proposed resolution:
This wording is relative to N4917.
Modify 24.3.9.5 [forward.list.modifiers] as indicated:
[Drafting note: emplace_front, push_front, and prepend_range are already covered by 24.2 [container.requirements]. ]
iterator insert_after(const_iterator position, const T& x);
-?- Preconditions: T is Cpp17CopyInsertable into forward_list. position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
-?- Effects: Inserts a copy of x after position.
-?- Returns: An iterator pointing to the copy of x.
iterator insert_after(const_iterator position, T&& x);
-6- Preconditions: T is Cpp17MoveInsertable into forward_list. position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
-7- Effects: Inserts a copy of x after position.
-8- Returns: An iterator pointing to the copy of x.
iterator insert_after(const_iterator position, size_type n, const T& x);
-9- Preconditions: T is Cpp17CopyInsertable into forward_list. position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
-10- Effects: Inserts n copies of x after position.
-11- Returns: An iterator pointing to the last inserted copy of x, or position if n == 0 is true.
template<class InputIterator> iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
-12- Preconditions: T is Cpp17EmplaceConstructible into forward_list from *first. position is before_begin() or is a dereferenceable iterator in the range [begin(), end()). Neither first nor last are iterators in *this.
-13- Effects: Inserts copies of elements in [first, last) after position.
-14- Returns: An iterator pointing to the last inserted element, or position if first == last is true.
template<container-compatible-range<T> R> iterator insert_after(const_iterator position, R&& rg);
-15- Preconditions: T is Cpp17EmplaceConstructible into forward_list from *ranges::begin(rg). position is before_begin() or is a dereferenceable iterator in the range [begin(), end()). rg and *this do not overlap.
-16- Effects: Inserts copies of elements in range rg after position.
-17- Returns: An iterator pointing to the last inserted element, or position if rg is empty.
iterator insert_after(const_iterator position, initializer_list<T> il);
-18- Effects: Equivalent to: return insert_after(position, il.begin(), il.end())
.;
-19- Returns: An iterator pointing to the last inserted element or position if il is empty.
template<class... Args> iterator emplace_after(const_iterator position, Args&&... args);
-20- Preconditions: T is Cpp17EmplaceConstructible into forward_list from std::forward<Args>(args).... position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
-21- Effects: Inserts an object of type value_type
constructeddirect-non-list-initialized withvalue_type(std::forward<Args>(args)...)after position.-22- Returns: An iterator pointing to the new object.