Dude, Where's My Bored Ape?

Released: June 21, 2022

IMPORTANT: This release deprecates views::group_by which was
an endless source of confusion. group_by is replaced with
views::chunk_by (which, beware, has subtly different semantics,
see below.)

Changes:

• NEW: views::chunk_by which, like the old views::group_by it replaces,
  splits a range into a range-of-ranges, where adjacent elements satisfy a binary
  predicate (#1648). [Note: Whereas views::group_by evaluated the predicate
  between the current element and the first element in the chunk, views::chunk_by
  evaluates the predicate between adjacent elements. -- end note]
• NEW: constexpr all the algorithms that are constexpr in C++20's std::ranges
  (#1683).
• NEW: Fold algorithms from P2322 (#1628), (#1668).
• NEW: ranges::unformatted_ostream_iterator (#1586).
• NEW: Support for the build2 build system (#1562).
• Implement P2328: relax the constraint on ranges::join_view
  to support joining ranges of prvalue non-view ranges (#1655).
• Improved algorithm for ranges::linear_distribute (#1679).
• Renamed safe_subrange_t to borrowed_subrange_t (#1542).
• Extend ranges::to to support conversion to container-of-containers (#1553).
• views::enumerate can be a borrowed_view (#1571).
• ranges::upper_bound works in the presence of overloaded operator& (#1632).
• Input iterators are no longer required to be default-constructible (#1652).

Bugs fixed:

• ranges::to<std::map>(v) does not work (#1700)
• ranges::reverse_iterator has the wrong value_type when reversing a proxy
  range (#1670).
• A post-increment of a ranges::counted_iterator wrapping an input iterator with
  a void-returning post-increment operator isn't incrementing the count (#1664).
• Bad assert in views::drop_last (#1599).
• Read of uninitialized bool in views::cache1 (#1610).
• ranges::unstable_remove_if calls predicate on same element twice (#1629).
• ranges::on(f,g)(x...) should be f(g(x)...) instead of f(g(x...)) (#1661).
• Broken qualification of cmake targets (#1557).
• Various portability and documentation fixes.

Credits: I would like to thank the following people who contributed to this release
(in no particular order): Barry Revzin, @dvirtz, Gonzalo Brito, Johel Ernesto Guerrero
Peña, Joël Lamotte, Doug Roeper, Facundo Tuesca, Vitaly Zaitsev, @23rd, @furkanusta,
Jonathan Haigh, @SmorkalovG, @marehr, Matt Beardsley, Chris Glover, Louis Dionne, Jin
Shang (@js8544), Hui Xie, @huixie90, Robert Maynard, Silver Zachara, @sergegers,
Théo DELRIEU, @LesnyRumcajs, Yehezkel Bernat, Maciej Patro, Klemens Nanni, Thomas
Madlener, and Jason Merrill.

🎉 Special thanks to Barry Revzin for stepping up to be part-time co-maintainer of
range-v3. 🎉

Thanks, ISO

Released: August 6, 2020

IMPORTANT: This release removes the heuristic that tries to guess whether a range type
is a "view" (lightweight, non-owning range), in accordance with the C++20. This is a
potentially source-breaking change. Code that previously used an rvalue range as the
start of a pipeline could stop compiling if the range library is not explicitly told that
that range type is a view. To override the new default, please specialize the
ranges::enable_view<R> Boolean variable template.

IMPORTANT: This release removes the implicit conversion from views to containers.
To construct a container from an arbitrary range, you must now explicitly use
ranges::to. For example, the following code no longer works:

std::vector<int> is = ranges::views::ints(0, 10); // ERROR: no conversion

Instead, please write this as:

auto is = ranges::views::ints(0, 10) | ranges::to<std::vector>; // OK

ranges::to lives in header <range/v3/range/conversion.hpp>

IMPORTANT: This release drops support for llvm-3.9.

Changes:

• NEW: A new concepts portability layer that short-circuits atomic constraints
  in requires clauses for better compile times when emulating concepts.
• NEW: Restored support for MSVC in /std:c++17 mode, and for MSVC's default preprocessor.
• Remove the implicit conversion from views to containers.
• Rename the following entities to be consistent with C++20's std::ranges support:
  • safe_range<R> -> borrowed_range<R>
  • enable_safe_range<R> -> enable_borrowed_range<R>
  • safe_iterator_t<R> -> borrowed_iterator_t<R>
  • safe_subrange_t<R> -> borrowed_subrange_t<R>
  • readable_traits<I> -> indirectly_readable_traits<I>
  • readable<I> -> indirectly_readable<I>
  • writable<I> -> indirectly_writable<I>
• Added the following to the ranges::cpp20 namespace:
  • Algorithm for_each_n
  • Algorithm sample
  • Class view_base
  • Alias views::all_t
• Type __int128 is recognized as "integer-like".
• Adds concepts three_way_comparable[_with] when <=> is supported.
• Adds concepts partially_ordered[_with].
• Better conformance with C++20's use of the boolean-testable concept.
• Support C++20 coroutines.
• Honor CMake's CMAKE_CXX_STANDARD variable.
• A fix for the cardinality of views::zip[_with] (#1486).
• Add view_interface::data() member function.
• Add necessary specializations for std::basic_common_reference and
  std::common_type.
• Numerous workarounds for MSVC.
• Various CMake fixes and improvements.
• drop_while_view is not a sized_range.
• Added support for Wind River Systems.
• Bug fixes to views::group_by (#1393).
• common_[reference|type] of common_[tuple|pair] now yields a common_[tuple|pair]
  instead of a std::[tuple|pair] (#1422).
• Avoid UB when currying an lvalue in some views and actions (#1320).

Credits: I would like to thank the following people who contributed to this release
(in no particular order): Christopher Di Bella, @marehr, Casey Carter, Dvir Yitzchaki,
Justin Riddell, Johel Ernesto Guerrero Peña, Barry Revzin, Kamlesh Kumar, and Vincas
Dargis.

To Err Is Human

Released: Dec 6, 2019.

IMPORTANT: Before upgrading, please note that several older compiler versions
and build configurations are no longer supported! In particular, MSVC now needs
/std:c++latest.

ALSO: When taking a dependency on the range-v3, meta, or concepts
libraries via CMake, please now use the namespace qualified target names:

• range-v3::range-v3
• range-v3::meta
• range-v3::concepts

Changes:

• NEW: Rewritten concepts portability layer with simpler macros for better
  diagnostics.
• NEW: The views::cache1 view caches the most recent value in the
  range. This can help avoid reevaluation of transformations in complex view
  pipelines.
• NEW: ranges::contains algorithm.
• NEW: enable_safe_range trait for opting in to the forwarding-range
  concept. These are ranges whose iterators remain valid even after the
  range itself has been destroyed; e.g., std::string_view and
  ranges::subrange.
• The readable concept has changed such that types that are not indirectly
  readable with operator* (_e.g., std::optional) no longer satisfy that
  concept.
• Using views::join to join a range of xvalue ranges works again.
• The following range access primitives no longer accept temporary containers
  (i.e., they refuse to return references known to be dangling):
  • range::front
  • range::back
  • range::at
  • range::index
• views::concat with a single argument now simply returns its argument.
• ranges::ostream_iterator<T> now coerces arguments to T before inserting
  them into the wrapped ostream.
• Smaller iterators for views::transform and views::take_while.
• actions::split and actions::split_when now support partial application and
  pipelining (#1085).
• views::group_by and its iterator both get a .base() member to access the
  underlying range and iterator, respectively.
• Improved diagnostics with clang.
• Assorted bug fixes and compiler work-arounds: #284, #491, #499, #871, #1022, #1043, #1081, #1085,
  #1101, #1116, #1296, #1305, and #1335.

Many thanks to GitHub users @CaseyCarter, @morinmorin, @h-2, @MichaelWJung,
@JohelEGP, @marehr, @alkino, @xuning97, @brevzin, and @mpusz for their
contributions.

Std::ranger Things

Released: Aug 26, 2019.

Bring many interfaces into sync with the C++20 draft.

• NEW: An improved concepts portability layer with macros that use C++20
  concepts when the compiler supports them.

• NEW: An improved directory structure that keeps disjoint parts of the
  library -- iterators, ranges, algorithms, actions, views, functional
  programming support, and general utilities -- physically separate.

• NEW: A RANGES_DEEP_STL_INTEGRATION configuration option that makes your
  STL implementation default to structural conformance to infer iterator
  category, as in C++20. Applies to libc++, libstdc++, and MSVC's Standard
  Library.

• NEW: A ranges::cpp20 namespace that contains all the functionality of
  C++20's std::ranges namespace.

• All concept names have been given standard_case (renamed from PascalCase) and
  have been harmonized with the C++20 draft.

• The following range access customization points no longer accept rvalue ranges
  by default:

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

• Iterators may specify an iterator_concept type alias in addition to
  iterator_category -- either as a nested type or as a member of a
  std::iterator_traits specialization -- to denote conformance to the C++20
  iterator concepts as distinct from the C++98 iterator requirements.
  (See P1037 "Deep Integration of the Ranges TS"
  for more information.)

• The ranges::value_type trait has been renamed to readable_traits.

• The ranges::difference_type trait has been renamed to incrementable_traits.

• The ranges::iterator_category trait has been deprecated. Specialize
  std::iterator_traits to non-intrusively specify an iterator's category
  and (optionally) concept.

• Rename the ranges::view namespace to ranges::views and ranges::action to
  ranges::actions (with deprecated namespace aliases for migration).

• Rename view::bounded to views::common.

• Rename unreachable to unreachable_sentinel_t.

• Change dangling from a class template that wraps an iterator to a class that
  acts as a placeholder for an iterator that would otherwise dangle.

• Implement C++20's subrange as a view that wraps an iterator/sentinel pair;
  deprecate iterator_range.

• Deprecate implicit conversion from view types to containers; rename
  ranges::to_ to ranges::to and extend it to support converting a
  range-of-ranges to a container-of-containers.

• Deprecate the ranges::v3 inline versioning namespace.

• The following views have had minor changes to bring them into conformance with
  the C++20 working draft:

  • join_view
  • single_view
  • empty_view
  • split_view
  • reverse_view
  • all_view
  • take_view
  • iota_view

  `iota_view`, in particular, is given a user-defined `difference_type` that avoids integer overflow.

• New names for the iterator and range type aliases:

  Old Name	New Name
  value_type_t	iter_value_t
  reference_t	iter_reference_t
  difference_type_t	iter_difference_t
  size_type_t	deprecated
  rvalue_reference_t	iter_rvalue_reference_t
  range_value_type_t	range_value_t
  range_difference_type_t	range_difference_t
  range_size_type_t	range_size_t

Hell freezes

• NEW: MSVC support, from @CaseyCarter 🎉 (See the docs for the list of supported compilers.)
• NEW: view::enumerate, from @MikeGitb
• NEW: view::addressof, from @tower120
• NEW: unstable_remove_if algorithm and action, from @tower120
• NEW: adjacent_remove_if algorithm and action, from @tower120
• NEW: ostream_joiner, from @sv1990
• view::drop_while and view::take_while get projection support, from @mrpi
• view::filter and view::remove_if get projection support, from @mrpi
• view::unique accepts optional comparison operator, from @tete17
• action::slice supports sliding from the end, from @tete17
• Support coroutines on MSVC, from @CaseyCarter
• Faster view::generate_n, from GitHub user @tower120
• Improved aligned new detection for libc++ on iOS, from @mtak-
• Various CMake improvements, from @JohelEGP
• view_adaptor supports basic_iterator-style mixins, from @tower120
• Fix ranges::advance for random-access iterators for n==0, from @tower120
• Bugs fixed: #755, #759, #942, #946, #952, #975, #978, #986, #996, #1041, #1047, #1088, #1094, #1107, #1129

0.4.0

0.4.0 Oct 18, 2018

• Minor interface-breaking changes:
  • single_view returns by const & (see #817).
  • reverse_view of a non-Sized, non-Bounded RandomAccess range (eg., a null-terminated string) no longer satisfies SizedRange.
  • The generate and generate_n views now return the generated values by xvalue reference (T &&) to the value cached within the view (see #905).
  • Views no longer prefer returning constant iterators when they can; some views have different constant and mutable iterators.
• Enhancements:
  • Views can successfully adapt other views that have different constant and mutable iterators.
  • The single, empty, and reverse views are much closer to the versions as specified in P0896.
• Bug fixes:
  • "single_view should not copy the value" #817.
  • "Calling back() on strided range does not return the correct last value in range" #901.
  • "generate(foo) | take(n) calls foo n+1 times" #819.
  • "generate seems broken with move-only return types" #905.
  • "Unexpected behavior in generate with return by reference" #807.
  • "Inconsistent behaviour of ranges::distance with ranges::view::zip using infinite views." #783.
  • "Infinite loop when using ranges::view::cycle with an infinite range" #780.
  • "Composing ranges::view::cycle with ranges::view::slice" #778.
  • "cartesian_product view, now with moar bugs." #919.

0.3.7

0.3.7 Sept 19, 2018

• Improved support for clang-cl (thanks to @CaseyCarter).
• Fix for any_view<T, category::sized | category::input> (see #869).
• Fix iter_move of a ranges::reverse_iterator (see #888).
• Fix move_sentinel comparisons (see #889).
• Avoid ambiguity created by boost::advance and std::advance (see #893).

0.3.6

• 0.3.6 May 15, 2018
  • NEW: view::exclusive_scan (thanks to GitHub user @mitsutaka-takeda).
  • All views get non-const overloads of .empty() and .size() (see ericniebler/stl2#793).
  • Upgrade Conan support for conan 1.0.
  • subspan interface tweaks.
  • Fix bug in view::split (see this stackoverflow question).
  • Fix bug in view::stride (see ericniebler/stl2#805).
  • Fix const-correctness problem in view::chunk (see this stackoverflow question).
  • Replace uses of ranges::result_of with ranges::invoke_result.
  • Fix potential buffer overrun of view::drop over RandomAccessRanges.
  • Lots of view::cartesian_product fixes (see ericniebler/stl2#820, ericniebler/stl2#823).
  • Work around gcc-8 regression regarding volatile std::initializer_lists (see ericniebler/stl2#826).
  • Fix const-correctness problem of view::take.

Version 0.3.5

0.3.5 February 17, 2018

• Rvalues may satisfy Writable (see ericniebler/stl2#387).
• view_interface gets a bounds-checking at method.
• chunk_view works on Input ranges.
• Fix bug in group_by_view.
• Improved concept checks for partial_sum numeric algorithm.
• Define ContiguousIterator concept and contiguous_iterator_tag iterator
  category tag.
• Sundry span fixes.
• action::insert avoids interfering with vector's exponentional growth
  strategy.
• Add an experimental shared view for views that need container-like scratch
  space to do their work.
• Faster, simpler reverse_view.
• Rework ranges::reference_wrapper to avoid LWG#2993.
• Reworked any_view, the type-erased view wrapper.
• equal algorithm is constexpr in C++14.
• stride_view no longer needs an atomic data member.
• const-correct drop_view.
• adjacent_filter_view supports bidirectional iteration.
• Massive view_adaptor cleanup to remove the need for a mutable data
  member holding the adapted view.
• Fix counting_iterator post-increment bug.
• tail_view of an empty range is an empty range, not undefined behavior.
• Various portability fixes for gcc and clang trunk.

0.3.0

0.3.0 June 30, 2017

• Input views may now be move-only (from @CaseyCarter)
• Input any_views are now much more efficient (from @CaseyCarter)
• Better support for systems lacking a working <thread> header (from @CaseyCarter)