P0896R4 <ranges>

[StephanTLavavej]

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

LWG-3169 ranges permutation generators discard useful information
LWG-3173 Enable CTAD for ref-view
LWG-3179 subrange should always model Range
LWG-3180 Inconsistently named return type for ranges::minmax_element
LWG-3183 Normative permission to specialize Ranges variable templates
LWG-3186 ranges removal, partition, and partial_sort_copy algorithms discard useful information
LWG-3191 std::ranges::shuffle synopsis does not match algorithm definition
LWG-3276 Class split_view::outer_iterator::value_type should inherit from view_interface
LWG-3280 View converting constructors can cause constraint recursion and are unneeded
LWG-3281 Conversion from pair-like types to subrange is a silent semantic promotion
LWG-3282 subrange converting constructor should disallow derived to base conversions
LWG-3286 ranges::size is not required to be valid after a call to ranges::begin on an input range
LWG-3291 iota_view::iterator has the wrong iterator_category
LWG-3292 iota_view is under-constrained
LWG-3299 Pointers don't need customized iterator behavior
LWG-3301 transform_view::iterator has incorrect iterator_category
LWG-3302 Range adaptor objects keys and values are unspecified
LWG-3313 join_view::iterator::operator-- is incorrectly constrained
LWG-3323 has-tuple-element helper concept needs convertible_to
LWG-3325 Constrain return type of transformation function for transform_view
LWG-3335 range_size_t and views::all_t
LWG-3355 The memory algorithms should support move-only input iterators introduced by P1207
LWG-3363 drop_while_view should opt-out of sized_range
LWG-3364 Initialize data members of ranges and their iterators
LWG-3381 begin and data must agree for contiguous_range
LWG-3384 transform_view::sentinel has an incorrect operator-
LWG-3385 common_iterator is not sufficiently constrained for non-copyable iterators
LWG-3387 [range.reverse.view] reverse_view<V> unintentionally requires range<const V>
LWG-3388 view iterator types have ill-formed <=> operators
LWG-3389 A move-only iterator still does not have a counted_iterator
LWG-3397 ranges::basic_istream_view::iterator should not provide iterator_category
LWG-3398 tuple_element_t is also wrong for const subrange
LWG-3474 Nesting join_views is broken because of CTAD
LWG-3500 join_view::iterator::operator->() is bogus
LWG-3505 split_view::outer-iterator::operator++ misspecified

Feature-test macro as of WG21-N4842, increased by WG21-P1902:
#define __cpp_lib_ranges 201911L

[CaseyCarter]

Detailed breakdown / rough plan-of-action for Ranges:

• WG21-P0898 "Standard Library Concepts"
  • Changes to common_type and addition of common_reference (MSVC-PR-179742)
  • Addition of <concepts> (with WG21-P0896's changes to Swappable/SwappableWith) (MSVC-PR-182506)
• Iterator machinery in <xutility> (MSVC-PR-194010)
  • Traits: incrementable_traits, readable_traits, iterator_traits
  • CPOs: iter_move, iter_swap
  • Aliases: iter_XXXX_t
  • Concepts: readable, writable, ... random_access_iterator, contiguous_iterator
  • WG21-P1207's changes to weakly_incrementable
  • WG21-P1754's concept renaming.
• Range machinery in <xutility> (Ranges <range> machinery #82)
  • CPOs: c?r?(begin|end), c?data, empty, size (WG21-P1523 changes)
  • Aliases: iterator_t, sentinel_t
  • WG21-P1035's range_XXXX_t composed aliases
  • Concepts: XXX_range, view, ...
  • WG21-P1474 changes to contiguous_iterator
• Update "old" range types (Update "old" range types #95)
  • to model contiguous_range: array, basic_string, basic_string_view, valarray, vector (not span yet - it's unimplemented)
  • and forwarding-range: basic_string_view (not span yet)
• More iterator machinery in <xutility> ([range.iter.ops], default_sentinel, and unreachable_sentinel #329)
  • Primitives: ranges::advance, ranges::next, ranges::prev, ranges::distance
  • default_sentinel
  • unreachable_sentinel
• Functional machinery
  • identity (MSVC-PR-167844)
  • ranges::equal_to and ranges::less in <xutility>, other ranges comparison function objects in <functional> (<compare>,<functional> Concept-constrained comparisons #385)
• Misc range concepts ([ranges] Implement some range concepts #389)
  • WG21-P1870 safe_range
  • Relax copyability requirement of view concept (Partially implements WG21-P1456 "Move-Only Views")
  • viewable_range concept
• Fix various issues with Range Access CPOs (investigation for WG21-P2091) (Implement fixes from D2091R0 "Issues with Range Access CPOs" #432)
• Algorithm machinery in <xutility> (Several range algorithms #565)
  • Indirect callable concepts / Common algorithm requirements
  • indirectly_swappable
  • projected
  • dangling, borrowed_iterator_t
  • WG21-P2106 generic algorithm result types
  • <algorithm>s batch 1:
    • copy/copy_n/copy_if
    • all_of/any_of/none_of
    • find/find_if/find_if_not
    • count/count_if
    • for_each/for_each_n
    • equal/mismatch
• LWG-3326 "enable_view has false positives" (enable_view<T> now defaults to derived_from<T, view_base> #588)
• insert iterators (P0896R4 changes to insert iterators #589)
• Iterator adaptors, old and new:
  • WG21-P1871 Rename disable_sized_sentinel to disable_sized_sentinel_for (P1871R1 disable_sized_sentinel_for #607)
  • stream iterators (P0896R4 stream iterator changes #1281)
  • reverse_iterator (C++20 reverse_iterator changes #759)
  • move_iterator (with WG21-P1252 operator-> deprecation), move_sentinel (WG21-P1207 changes) (C++20 move_iterator changes and move_sentinel #787)
  • common_iterator (Implement common_iterator #1092)
  • counted_iterator (Implement counted_iterator #1083)
  • Strengthen noexcept on all of the above
• view_interface, subrange, borrowed_subrange_t (Implement ranges::subrange and ranges::view_interface #734)
• Many range <algorithm>s
  • find_end (Implement ranges::find_end #815)
  • find_first_of (Implement ranges::find_first_of #821)
  • adjacent_find (Implement ranges::adjacent_find #822)
  • is_permutation (Implement ranges::is_permutation #892)
  • search (Implement ranges::search #896)
  • search_n (Implement ranges::search_n #914)
  • copy_backward (Implement ranges::copy_backward #1026)
  • move (<algorithm>: Implemented ranges::move #888)
  • move_backward (Implement ranges::move_backward #1053)
  • swap_ranges (Implement ranges::swap_ranges #918)
  • transform (Implement ranges::transform #941)
  • replace, replace_copy, replace_copy_if (Implement ranges::replace #983)
  • replace_if (Implement ranges::replace_if #984)
  • fill, fill_n (Implement ranges::fill and ranges::fill_n #904)
  • generate, generate_n (Implement ranges::generate and ranges::generate_n #905)
  • remove, remove_if, remove_copy, remove_copy_if (Implement ranges::remove family #1005)
  • unique, unique_copy (Implement ranges::unique family #1039)
  • reverse (Implement ranges::reverse #1028)
  • reverse_copy (Implement ranges::reverse_copy #1095)
  • rotate, rotate_copy (Implement ranges::rotate and ranges::rotate_copy #1073)
  • sample, shuffle (Implement ranges::sample and ranges::shuffle #1052)
  • sort (Implement ranges::sort #1127)
  • partial_sort, partial_sort_copy (Implement ranges::partial_sort and ranges::partial_sort_copy #1231)
  • is_sorted, is_sorted_until (Implement ranges::is_sorted and ranges::is_sorted_until #915)
  • nth_element (Implement ranges::nth_element #1063)
  • lower_bound, upper_bound, equal_range, binary_search (Implement the "binary search" ranges algorithm family #917)
  • is_partitioned, partition, partition_copy, partition_point (Implement most ranges partition algorithms #976)
  • merge (Implement ranges::merge #1101)
  • stable_partition, inplace_merge, stable_sort (Implement allocating algorithms for ranges #1383)
  • includes, set_union, set_intersection, set_difference, set_symmetric_difference (Implement Ranges Set Operations #1044)
  • push_heap, pop_heap, make_heap, sort_heap, is_heap, is_heap_until (Implement ranges heap algorithms #930)
  • min, max, minmax, clamp, min_element, max_element, minmax_element (Implement ranges min/max/minmax algorithms #916)
  • lexicographical_compare (Implement ranges::lexicographical_compare #1081)
  • next_permutation, prev_permutation (Implement ranges::next_permutation and ranges::prev_permutation #1099)
• ranges::ssize (Implement ranges::ssize #1076)
• Range factories in <ranges>:
  • empty_view, single_view, semiregular-box (Implement views::empty and views::single range factories #1201)
  • iota_view (Implement ranges::iota_view #1693)
  • basic_istream_view (Implement ranges::istream_view #1334)
• Range adaptor machinery
  • ref_view (Implement ranges::ref_view #1132)
  • views::all, views::all_t, |, reverse_view (Implement views::all and views::reverse #1229)
• Range adaptors
  • filter_view (Implement views::filter #1252)
  • views::counted (Implement views::counted #1375)
  • transform_view (Implement views::transform #1258)
  • drop_view, take_view (Implement views::take and views::drop #1253)
  • Integrate P1391R4 into views::drop and views::take (Integrate P1391 into views::take and views::drop #1271)
  • drop_while_view (Implement drop_while_view #1366)
  • take_while_view (Implement ranges::take_while_view #1372)
  • elements_view (keys_view, values_view) (Implement ranges::elements_view #1406)
  • common_view (Implement ranges::common_view #1305)
  • join_view (Implement ranges::join_view #1436)
  • split_view (Implement ranges::split_view #1731)
• Specialized <memory> range algorithms
  • Special memory concepts, uninitialized_move (Implement ranges::uninitialized_move #1137)
  • uninitialized_copy, uninitialized_copy_n, uninitialized_default_construct, uninitialized_default_construct_n, uninitialized_fill, uninitialized_fill_n, uninitialized_move_n, uninitialized_value_construct, uninitialized_value_construct_n (Implement ranges::uninitialized_meow #1164)
  • destroy_at, construct_at (Minimal changes to support constexpr allocation in MSVC #1313)
• Odds and ends:
  • P1391R4 Range Constructor For string_view ( P1391R4 "Range Constructor for string_view" #1245)
• Audit <=> for [ranges] (all done, except for join_view and split_view which are being implemented, and P1614R2 Adding Spaceship <=> To The Library #1678 fixed take_view::sentinel's operator==)
• Define __cpp_lib_ranges (Define __cpp_lib_ranges #1748)