* Implement constexpr algorithms.
Resolves GH-6 ( P0202R3 ), resolves GH-38 ( P0879R0 ), and drive-by fixes GH-414.
Everywhere: Add constexpr, _CONSTEXPR20, and _CONSTEXPR20_ICE to things.
skipped_tests.txt: Turn on all tests previously blocked by missing constexpr algorithms (and exchange and swap). Mark those algorithms that cannot be turned on that we have outstanding PRs for with their associated PRs.
yvals_core.h: Turn on feature test macros.
xutility:
* Move the _Ptr_cat family down to copy, and fix associated SHOUTY comments to indicate that this is really an implementation detail of copy, not something the rest of the standard library intends to use directly. Removed and clarified some of the comments as requested by Casey Carter.
* Extract _Copy_n_core which implements copy_n using only the core language (rather than memcpy-as-an-intrinsic). Note that we cannot use __builtin_memcpy or similar to avoid the is_constant_evaluated check here; builtin_memcpy only works in constexpr contexts when the inputs are of type char.
numeric: Refactor as suggested by GH-414.
* Attempt alternate fix of GH-414 suggested by Stephan.
* Stephan product code PR comments:
* _Swap_ranges_unchecked => _CONSTEXPR20
* _Idl_dist_add => _NODISCARD (and remove comments)
* is_permutation => _NODISCARD
* Add yvals_core.h comments.
* Delete unused _Copy_n_core and TRANSITION, DevCom-889321 comment.
* Put the comments in the right place and remove phantom braces.
Implements iterator primitive operations `std::ranges::advance`, `std::ranges::next`, `std::ranges::prev`, and `std::ranges::distance`; as well as `std::default_sentinel` and `std::unreachable_sentinel`.
This change reworks the STL's iterator unwrapping machinery to enable unwrapping of C++20 move-only single-pass iterators (and `if constepxr`s all the things). Consequently, `_Iter_ref_t`, `_Iter_value_t`, and `_Iter_diff_t` resolve to `iter_reference_t`, `iter_value_t`, and `iter_difference_t` (respectively) in `__cpp_lib_concepts` (soon to be C++20) mode. This change necessitates some fixes to `unique_copy` and `_Fill_memset_is_safe` which both assume that `_Iter_value_t<T>` is well-formed for any iterator `T`. (`iter_value_t<T>` does not have that property: it is only well-formed when `readable<T>`.)
I notably haven't unified `default_sentinel_t` with `_Default_sentinel` out of an abundance of paranoia. Our `move_iterator` is comparable with `_Default_sentinel`, which is not the case for `std::default_sentinel`.
Drive-by:
* This change `if constexpr`-izes `unique_copy`.
Resolves#55.
* Deprecate experimental::erase
* Implement P1209R0
* Update yvals_core.h
* Update deprecations and remove <experimental/xutility>
* move and reorder erase/erase_if
* moved _Erase and remove and friends to <xmemory>
* Consistently place erase_if() definitions.
* 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](https://wg21.link/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`"](https://wg21.link/p1474r1):
* 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>`
Michael Schellenberger Costa
Billy O'Neal
Daniel Marshall
Casey Carter
Nathan Ward
Stephan T. Lavavej
Casey Carter