Range-v3
Range algorithms, views, and actions for the Standard Library
Release Notes

Version 0.12.0 "Dude, Where's My Bored Ape?"

Released: June 19, 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.

&#127881; Special thanks to Barry Revzin for stepping up to be part-time co-maintainer of range-v3. &#127881;

Version 0.11.0 "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:

‍

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

Instead, please write this as:

{c++}
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.

Version 0.10.0 "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-v3meta
  • 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.

Version 0.9.1

Released: Sept 1, 2019.

gcc-9.x portability fixes.

Version 0.9.0 "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<std::[u]intmax_t>, 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

Version 0.5.0

Released: Apr 30, 2019.

  • NEW: MSVC support, from @CaseyCarter :tada: (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 @cjdb
  • 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

Version 0.4.0

Released: 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 and empty 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.

Version 0.3.7

Released: 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).

Version 0.3.6

Released: May 15, 2018.

Version 0.3.5

Released: 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.

Version 0.3.0

Released: 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)

Version 0.2.6

Released: June 21, 2017.

  • Experimental coroutines with ranges::experimental::generator (from @CaseyCarter)
  • ranges::optional now behaves like std::optional (from @CaseyCarter)
  • Extensive bug fixes with Input ranges (from @CaseyCarter)

Version 0.2.5

Released: May 16, 2017.

  • view::chunk works on Input ranges (from @CaseyCarter)
  • for_each_n algorithm (from @khlebnikov)
  • Portability fixes for MinGW, clang-3.6 and -3.7, and gcc-7; and cmake 3.0

Version 0.2.4

Released: April 12, 2017.

Fix the following bug:

  • action::stable_sort of vector broken on Clang 3.8.1 since ~last Xmas (ericniebler/range-v3#632).

Version 0.2.3

Released: April 4, 2017.

Fix the following bug:

  • iterators that return move-only types by value do not satisfy Readable (ericniebler/stl2#399).

Version 0.2.2

Released: March 30, 2017.

New in this release:

  • view::linear_distribute(from,to,n) - A view of n elements between from and to, distributed evenly.
  • view::indices(n) - A view of the indices [0,1,2...n-1].
  • view::closed_indices(n) - A view of the indices [0,1,2...n].

This release deprecates view::ints(n) as confusing to new users.

Version 0.2.1

Released: March 22, 2017.

New in this release:

  • view::cartesian_product
  • action::reverse

Version 0.2.0

Released: March 13, 2017.

Bring many interfaces into sync with the Ranges TS.

  • Many interfaces are simply renamed. The following table shows the old names and the new. (All names are in the ranges::v3 namespace.)
    Old Name New Name
    indirect_swap iter_swap
    indirect_move iter_move
    iterator_value_t value_type_t
    iterator_reference_t reference_t
    iterator_difference_t difference_type_t
    iterator_size_t size_type_t
    iterator_rvalue_reference_t rvalue_reference_t
    iterator_common_reference_t iter_common_reference_t
    range_value_t range_value_type_t
    range_difference_t range_difference_type_t
    range_size_t range_size_type_t
    range_iterator_t iterator_t
    range_sentinel_t sentinel_t
  • common_iterator now requires that its two types (Iterator and Sentinel) are different. Use common_iterator_t<I, S> to get the old behavior (i.e., if the two types are the same, it is an alias for I; otherwise, it is common_iterator<I, S>).
  • The following iterator adaptors now work with iterators that return proxies from their postfix increment operator (i.e., operator++(int)):
    • common_iterator
    • counted_iterator

  • The following customization points are now implemented per the Ranges TS spec and will no longer find the associated unconstrained overload in namespace std:::

    • ranges::begin
    • ranges::end
    • ranges::size
    • ranges::swap
    • ranges::iter_swap

    (In practice, this has very little effect but it may effect overloading in rare situations.)

  • ranges::is_swappable now only takes one template parameter. The new ranges::is_swappable_with<T, U> tests whether T and U are swappable. ranges::is_swappable<T> is equivalent to ranges::is_swappable_with<T &, T &>.
  • The following object concepts have changed to conform with the Ranges TS specification, and approved changes (see P0547):
    • Destructible
    • Constructible
    • DefaultConstructible
    • MoveConstructible
    • MoveConstructible
    • Movable
    • Assignable
  • The View concept is no longer satisfied by reference types.
  • The syntax for defining a concept has changed slightly. See iterator/concepts.hpp for examples.

Version 0.1.1

  • Small tweak to Writable concept to fix #537.

Version 0.1.0

  • March 8, 2017, Begin semantic versioning