libc++ Ranges Status

Overview

This document contains the status of the C++20 Ranges library in libc++. It is used to track both the status of the sub-projects of the ranges library and who is assigned to these sub-projects. This is imperative to effective implementation so that work is not duplicated and implementors are not blocked by each other.

If you are interested in contributing to the libc++ Ranges library, please send a message to the #libcxx channel in the LLVM discord. Please do not start working on any of the assigned items below.

Sub-Projects in the One Ranges Proposal

Section	Description	Dependencies	Assignee	Complete
[tuple.helper]	Update <tuple> includes.	None	Unassigned	Not started
[range.cmp]	ranges::equal_to ranges::not_equal_to ranges::less ranges::greater ranges::less_equal ranges::greater_equal	None	Zoe Carver	✅
[readable.traits]	indirectly_readable_traits iter_value_t	None	Christopher Di Bella	✅
[incrementable.traits]	incrementable_traits iter_difference_t		Christopher Di Bella	✅
[iterator.traits]	Updates to iterator_traits	indirectly_readable_traits incrementable_traits	Christopher Di Bella	✅
[special.mem.concepts]	no-throw-input-iterator no-throw-sentinel-for no-throw-input-range no-throw-forward-iterator no-throw-forward-range	[iterator.concepts] [range.refinements]	Unassigned	Not started
[specialized.algorithms]	ranges::uninitialized_default_construct ranges::uninitialized_default_construct_n ranges::uninitialized_value_construct ranges::uninitialized_value_construct_n ranges::uninitialized_copy ranges::uninitialized_copy_n ranges::uninitialized_move ranges::uninitialized_move_n ranges::uninitialized_fill ranges::uninitialized_fill_n ranges::construct_at ranges::destroy ranges::destroy_at ranges::destroy_n	[special.mem.concepts]	Unassigned	Not started
[strings]	Adds begin/end and updates const_iterator.	[iterator.concepts]	Unassigned	Not started
[views.span]	Same as [strings]	[iterator.concepts]	Unassigned	Not started
[iterator.cust.move]	ranges::iter_move		Zoe Carver	✅
[iterator.cust.swap]	ranges::iter_swap	iter_value_t	Zoe Carver	✅
[iterator.concepts]	indirectly_readable indirectly_writable weakly_incrementable incrementable input_or_output_iterator sentinel_for sized_sentinel_for input_iterator output_iterator forward_iterator bidirectional_iterator random_access_iterator contiguous_iterator		Various	✅
[indirectcallable.indirectinvocable]	indirectly_unary_invocable indirectly_regular_unary_invocable indirectly_unary_predicate indirectly_binary_predicate indirectly_equivalence_relation indirectly_strict_weak_order	[readable.traits]	Louis Dionne	✅
[projected]	ranges::projected	[iterator.concepts]	Louis Dionne	✅
[common.alg.req]: pt. 1	indirectly_movable indirectly_movable_storable indirectly_copyable indirectly_copyable_storable	[iterator.concepts]	Zoe Carver	In progress
[common.alg.req]: pt. 2	indirectly_swappable	[iterator.concepts] [iterator.cust.swap]	Zoe Carver	✅
[common.alg.req]: pt. 3	indirectly_comparable	[projected]	Louis Dionne	Not started
[common.alg.req]: pt. 4	permutable mergeable sortable	[iterator.concepts]	Unassigned	Not started
[std.iterator.tags]		[iterator.traits]	Unassigned	Not started
[range.iter.ops]	ranges::advance ranges::distance ranges::next ranges::prev	[iterator.concepts]	Christopher Di Bella	In progress
[predef.iterators]	Updates to predefined iterators.	[iterator.concepts] [iterator.cust.swap] [iterator.cust.move]	Unassigned	Not started
[move.sentinel]		[predef.iterators]	Unassigned	Not started
[common.iterator]		[iterator.concepts] [iterator.cust.swap] [iterator.cust.move]	Zoe Carver	✅
[default.sentinels]	std::default_sentinel_t.	No dependencies	Zoe Carver	✅
[counted.iterator]		[iterator.concepts] [iterator.cust.swap] [iterator.cust.move] [default.sentinels]	Zoe Carver	✅
[stream.iterators]		[default.sentinels]	Unassigned	Not started
[range.access]	ranges::begin ranges::end range::cbegin ranges::cend ranges::rbegin ranges::rend ranges::crbegin ranges::crend ranges::size ranges::ssize ranges::empty ranges::data ranges::cdata	[iterator.concepts]	Christopher Di Bella and Zoe Carver	In progress
[range.range]	ranges::range ranges::borrowed_range ranges::enable_borrowed_range ranges::iterator_t ranges::sentinel_t ranges::range_difference_t ranges::range_size_t ranges::range_value_t ranges::range_reference_t ranges::range_rvalue_reference_t	[range.access]	Christopher Di Bella	✅
[range.sized]	ranges::sized_range ranges::disable_sized_range	[range.primitives] [range.range]	Christopher Di Bella	✅
[range.view]	ranges::enable_view ranges::view_base ranges::view	[range.range]	Louis Dionne	✅
[range.refinements]	ranges::output_range ranges::input_range ranges::forward_range: `D100275 ranges::bidirectional_range ranges::random_access_range ranges::contiguous_range ranges::common_range	[range.range]	Christopher Di Bella	✅
[range.refinements]	ranges::viewable_range	[range.range]	Louis Dionne	✅
[range.utility.helpers]	simple-view has-arrow not-same-as	[range.range] [iterator.concept.input]	Zoe Carver	✅
[view.interface]	ranges::view_interface	[ranges.range] [range.view] [range.iterator.op.prev] [range.refinements]	Zoe Carver	✅
[range.subrange]	ranges::subrange	[view.interface]	Zoe Carver	✅
[range.dangling]	ranges::dangling ranges::borrowed_iterator_t ranges::borrowed_subrange_t	[range.range] [range.subrange]	Christopher Di Bella	✅
[range.all]	view::all	[range.subrange], [range.view.ref]	Zoe Carver	✅
[range.view.ref]	ref-view	[view.interface]	Zoe Carver	✅
[range.filter]	filter_view	[range.all]	Louis Dionne	Not started
[range.transform]	transform_view	[range.all]	Zoe Carver	✅
[range.iota]	iota_view	[range.all]	Louis Dionne	Not started
[range.take]	take_view	[range.all]	Zoe Carver	In Progress
[range.join]	join_view	[range.all]	Christopher Di Bella	Not started
[range.empty]	empty_view	[view.interface]	Zoe Carver	✅
[range.single]	single_view	[view.interface]	Zoe Carver	In Progress
[range.split]	split_view	[range.all]	Unassigned	Not started
[range.counted]	view::counted	[range.subrange]	Zoe Carver	Not started
[range.common]	common_view	[range.all]	Zoe Carver	✅
[range.reverse]	reverse_view	[range.all]	Unassigned	Not started

Misc. Items and TODOs

(Note: files with required updates will contain the TODO at the beginning of the list item so they can be easily found via global search.)

• TODO(XX_SPACESHIP_CONCEPTS): when spaceship support is added to various STL types, we need to update some concept tests.

Paper and Issue Status

(Note: stolen from MSVC here.)

Number	Name	Status	Assignee
P0896R4	<ranges>
P1035R7	Input Range Adaptors
P1207R4	Movability Of Single-Pass Iterators
P1243R4	Rangify New Algorithms
P1248R1	Fixing Relations
P1252R2	Ranges Design Cleanup
P1391R4	Range Constructor For string_view
P1456R1	Move-Only Views
P1474R1	Helpful Pointers For contiguous_iterator
P1522R1	Iterator Difference Type And Integer Overflow
P1523R1	Views And Size Types
P1638R1	basic_istream_view::iterator Should Not Be Copyable
P1716R3	Range Comparison Algorithms Are Over-Constrained
P1739R4	Avoiding Template Bloat For Ranges
P1862R1	Range Adaptors For Non-Copyable Iterators
P1870R1	safe_range
P1871R1	disable_sized_sentinel_for
P1878R1	Constraining Readable Types
P1970R2	ranges::ssize
P1983R0	Fixing Minor Ranges Issues
P1994R1	elements_view Needs Its Own sentinel
P2091R0	Fixing Issues With Range Access CPOs
P2106R0	Range Algorithm Result Types
P2325R3	Views should not be required to be default constructible
P2328R1	join_view should join all views of ranges
P2210R2	Superior String Splitting
P2281R1	Clarifying range adaptor objects
P2367R0	Remove misuses of list-initialization from Clause 24
LWG3169	ranges permutation generators discard useful information
LWG3173	Enable CTAD for ref-view
LWG3179	subrange should always model Range
LWG3180	Inconsistently named return type for ranges::minmax_element
LWG3183	Normative permission to specialize Ranges variable templates
LWG3186	ranges removal, partition, and partial_sort_copy algorithms discard useful information
LWG3191	std::ranges::shuffle synopsis does not match algorithm definition
LWG3276	Class split_view::outer_iterator::value_type should inherit from view_interface
LWG3280	View converting constructors can cause constraint recursion and are unneeded
LWG3281	Conversion from pair-like types to subrange is a silent semantic promotion
LWG3282	subrange converting constructor should disallow derived to base conversions
LWG3286	ranges::size is not required to be valid after a call to ranges::begin on an input range
LWG3291	iota_view::iterator has the wrong iterator_category
LWG3292	iota_view is under-constrained
LWG3299	Pointers don’t need customized iterator behavior
LWG3301	transform_view::iterator has incorrect iterator_category
LWG3302	Range adaptor objects keys and values are unspecified
LWG3313	join_view::iterator::operator– is incorrectly constrained
LWG3323	has-tuple-element helper concept needs convertible_to
LWG3325	Constrain return type of transformation function for transform_view
LWG3335	range_size_t and views::all_t
LWG3355	The memory algorithms should support move-only input iterators introduced by P1207
LWG3363	drop_while_view should opt-out of sized_range
LWG3364	Initialize data members of ranges and their iterators
LWG3381	begin and data must agree for contiguous_range
LWG3384	transform_view::sentinel has an incorrect operator-
LWG3385	common_iterator is not sufficiently constrained for non-copyable iterators
LWG3387	[range.reverse.view] reverse_view<V> unintentionally requires range<const V>
LWG3388	view iterator types have ill-formed <=> operators
LWG3389	A move-only iterator still does not have a counted_iterator
LWG3397	ranges::basic_istream_view::iterator should not provide iterator_category
LWG3398	tuple_element_t is also wrong for const subrange
LWG3474	Nesting join_views is broken because of CTAD
LWG3481	viewable_range mishandles lvalue move-only views
LWG3500	join_view::iterator::operator->() is bogus
LWG3505	split_view::outer-iterator::operator++ misspecified
LWG3517	join_view::iterator’s iter_swap is underconstrained
LWG3520	iter_move and iter_swap are inconsistent for transform_view::iterator
LWG3522	Missing requirement on InputIterator template parameter for priority_queue constructors
LWG3523	iota_view::sentinel is not always iota_view’s sentinel
LWG3532	split_view<V, P>::inner-iterator<true>::operator++(int) should depend on Base
LWG3533	Make base() const & consistent across iterator wrappers that supports input_iterators
LWG3541	indirectly_readable_traits should be SFINAE-friendly for all types
LWG3543	Definition of when counted_iterators refer to the same sequence isn’t quite right
LWG3546	common_iterator’s postfix-proxy is not quite right
LWG3549	view_interface is overspecified to derive from view_base
LWG3551	borrowed_{iterator,subrange}_t are overspecified
LWG3553	Useless constraint in split_view::outer-iterator::value_type::begin()
LWG3555	{transform,elements}_view::iterator::iterator_concept should consider const-qualification of the underlying range