Ranges <range> machinery

[CaseyCarter]

This is a port of Microsoft-internal PR 200667. [This info is a convenience for internal reviewers, it is NOT part of the commit log.]

Ranges machinery

• Implements a selection of support machinery in std::ranges and adds the <ranges> header. Primarily consists of the range access customization point objects:

  • ranges::begin
  • ranges::end
  • ranges::cbegin
  • ranges::cend
  • ranges::rbegin
  • ranges::rend
  • ranges::crbegin
  • ranges::crend
  • ranges::size
  • ranges::empty
  • ranges::data
  • ranges::cdata

  and range concepts:

  • ranges::range
  • ranges::output_range
  • ranges::input_range
  • ranges::forward_range
  • ranges::bidirectional_range
  • ranges::random_access_range
  • ranges::contiguous_range
  • ranges::sized_range
  • ranges::view
  • ranges::common_range

  and the associated type aliases:

  • ranges::iterator_t
  • ranges::sentinel_t
  • ranges::range_value_t
  • ranges::range_reference_t
  • ranges::range_difference_t
  • ranges::range_rvalue_reference_t

• Adds <ranges> - which is mostly empty since the support machinery is defined in <xutility> so as to be visible to <algorithm>

• Annotates P0896R4 as partially implemented in the "_HAS_CXX20 directly controls" section of <yvals_core.h>.

• Touches <regex>, <set>, and <unordered_set> to add partial specializations of ranges::enable_view for match_results and (unordered_)?multi?set as mandated by the WD to override the heuristic.

• Partially implements P1474R1 "Helpful pointers for ContiguousIterator":

  • Push pointer_traits from <xmemory> and to_address from <memory> up into <xutility>
  • Add to_address expression requirement to contiguous_iterator concept, and update P0896R4_ranges_iterator_machinery appropriately
  • Implement the changes to ranges::data (but not view_interface since it isn't yet implemented)

• Drive-by:

  • Simplify the definition of pointer_traits::_Reftype by eschewing add_lvalue_reference_t.
  • Strengthen reverse_iterator's constructors and make_reverse_iterator so ranges::rbegin and ranges::rend can be noexcept in more cases
  • Since we're using _Rng as the template parameter name for models of std::ranges::range, rename a local variable _Rng to _Generator in <random>

[StephanTLavavej]

Your description says "Annotate P0896R4 as partially implemented in the "_HAS_CXX20 indirect" section of <yvals_core.h>." but you're actually coalescing that section away.

Also, consider hyperlinking P1474R1 in the description.

Otherwise, looks good to me.

[CaseyCarter]

Your description says "Annotate P0896R4 as partially implemented in the "_HAS_CXX20 indirect" section of <yvals_core.h>." but you're actually coalescing that section away.

Corrected.

Also, consider hyperlinking P1474R1 in the description.

I've hyperlinked both P1474R1 and P0896R4. (And updated both the actual commit log and the description above.)