Re: [PATCH 5/5] libstdc++: Implement new views::split as per P2210

[Jonathan Wakely <jwakely@redhat.com>]

On Thu, 17 Jun 2021 at 16:59, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> This implements the new views::split as specified by P2210R2 "Superior
> string splitting".
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ranges (__non_propagating_cache::operator bool):
>         Define.
>         (split_view): Define as per P2210.
>         (views::__detail::__can_split_view): Define.
>         (views::_Split, views::Split): Define.
>         * testsuite/std/ranges/adaptors/100577.cc (test01, test02):
>         Test views::split.
>         * testsuite/std/ranges/adaptors/split.cc: New test.
>         * testsuite/std/ranges/p2325.cc (test08a): New test.
>         * testsuite/std/ranges/p2367.cc (test01): Test views::split.


OK



> ---
>  libstdc++-v3/include/std/ranges               | 205 ++++++++++++++++++
>  .../testsuite/std/ranges/adaptors/100577.cc   |  16 +-
>  .../testsuite/std/ranges/adaptors/split.cc    | 196 +++++++++++++++++
>  libstdc++-v3/testsuite/std/ranges/p2325.cc    |  14 ++
>  libstdc++-v3/testsuite/std/ranges/p2367.cc    |   1 +
>  5 files changed, 430 insertions(+), 2 deletions(-)
>  create mode 100644 libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index 78562924bee..42278f128b8 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -1195,6 +1195,10 @@ namespace views::__adaptor
>           return *this;
>         }
>
> +       constexpr explicit
> +       operator bool() const noexcept
> +       { return this->_M_is_engaged(); }
> +
>         constexpr _Tp&
>         operator*() noexcept
>         { return this->_M_get(); }
> @@ -3278,6 +3282,207 @@ namespace views::__adaptor
>      inline constexpr _LazySplit lazy_split;
>    } // namespace views
>
> +  template<forward_range _Vp, forward_range _Pattern>
> +    requires view<_Vp> && view<_Pattern>
> +      && indirectly_comparable<iterator_t<_Vp>, iterator_t<_Pattern>,
> +                              ranges::equal_to>
> +  class split_view : public view_interface<split_view<_Vp, _Pattern>>
> +  {
> +  private:
> +    _Pattern _M_pattern = _Pattern();
> +    __detail::__non_propagating_cache<subrange<iterator_t<_Vp>>> _M_cached_begin;
> +    _Vp _M_base = _Vp();
> +
> +    struct _Iterator;
> +    struct _Sentinel;
> +
> +  public:
> +    split_view() requires (default_initializable<_Vp>
> +                          && default_initializable<_Pattern>)
> +      = default;
> +
> +    constexpr
> +    split_view(_Vp __base, _Pattern __pattern)
> +      : _M_pattern(std::move(__pattern)),
> +       _M_base(std::move(__base))
> +    { }
> +
> +    template<forward_range _Range>
> +      requires constructible_from<_Vp, views::all_t<_Range>>
> +       && constructible_from<_Pattern, single_view<range_value_t<_Range>>>
> +    constexpr
> +    split_view(_Range&& __r, range_value_t<_Range> __e)
> +      : _M_pattern(views::single(__e)),
> +       _M_base(views::all(std::forward<_Range>(__r)))
> +    { }
> +
> +    constexpr _Vp
> +    base() const& requires copyable<_Vp>
> +    { return _M_base; }
> +
> +    constexpr _Vp
> +    base() &&
> +    { return std::move(_M_base); }
> +
> +    constexpr _Iterator
> +    begin()
> +    {
> +      if (!_M_cached_begin)
> +       _M_cached_begin = _M_find_next(ranges::begin(_M_base));
> +      return {this, ranges::begin(_M_base), *_M_cached_begin};
> +    }
> +
> +    constexpr auto
> +    end()
> +    {
> +      if constexpr (common_range<_Vp>)
> +       return _Iterator{this, ranges::end(_M_base), {}};
> +      else
> +       return _Sentinel{this};
> +    }
> +
> +    constexpr subrange<iterator_t<_Vp>>
> +    _M_find_next(iterator_t<_Vp> __it)
> +    {
> +      auto [__b, __e] = ranges::search(subrange(__it, ranges::end(_M_base)), _M_pattern);
> +      if (__b != ranges::end(_M_base) && ranges::empty(_M_pattern))
> +       {
> +         ++__b;
> +         ++__e;
> +       }
> +      return {__b, __e};
> +    }
> +
> +  private:
> +    struct _Iterator
> +    {
> +    private:
> +      split_view* _M_parent = nullptr;
> +      iterator_t<_Vp> _M_cur = iterator_t<_Vp>();
> +      subrange<iterator_t<_Vp>> _M_next = subrange<iterator_t<_Vp>>();
> +      bool _M_trailing_empty = false;
> +
> +    public:
> +      using iterator_concept = forward_iterator_tag;
> +      using iterator_category = input_iterator_tag;
> +      using value_type = subrange<iterator_t<_Vp>>;
> +      using difference_type = range_difference_t<_Vp>;
> +
> +      _Iterator() requires default_initializable<iterator_t<_Vp>> = default;
> +
> +      constexpr
> +      _Iterator(split_view* __parent,
> +               iterator_t<_Vp> __current,
> +               subrange<iterator_t<_Vp>> __next)
> +       : _M_parent(__parent),
> +         _M_cur(std::move(__current)),
> +         _M_next(std::move(__next))
> +      { }
> +
> +      constexpr iterator_t<_Vp>
> +      base() const
> +      { return _M_cur; }
> +
> +      constexpr value_type
> +      operator*() const
> +      { return {_M_cur, _M_next.begin()}; }
> +
> +      constexpr _Iterator&
> +      operator++()
> +      {
> +       _M_cur = _M_next.begin();
> +       if (_M_cur != ranges::end(_M_parent->_M_base))
> +         {
> +           _M_cur = _M_next.end();
> +           if (_M_cur == ranges::end(_M_parent->_M_base))
> +             {
> +               _M_trailing_empty = true;
> +               _M_next = {_M_cur, _M_cur};
> +             }
> +           else
> +             _M_next = _M_parent->_M_find_next(_M_cur);
> +         }
> +       else
> +         _M_trailing_empty = false;
> +       return *this;
> +      }
> +
> +      constexpr _Iterator
> +      operator++(int)
> +      {
> +       auto __tmp = *this;
> +       ++*this;
> +       return __tmp;
> +      }
> +
> +      friend constexpr bool
> +      operator==(const _Iterator& __x, const _Iterator& __y)
> +      {
> +       return __x._M_cur == __y._M_cur
> +         && __x._M_trailing_empty == __y._M_trailing_empty;
> +      }
> +
> +      friend struct _Sentinel;
> +    };
> +
> +    struct _Sentinel
> +    {
> +    private:
> +      sentinel_t<_Vp> _M_end = sentinel_t<_Vp>();
> +
> +      constexpr bool
> +      _M_equal(const _Iterator& __x) const
> +      { return __x._M_cur == _M_end && !__x._M_trailing_empty; }
> +
> +    public:
> +      constexpr explicit
> +      _Sentinel(split_view* __parent)
> +       : _M_end(ranges::end(__parent->_M_base))
> +      { }
> +
> +      friend constexpr bool
> +      operator==(const _Iterator& __x, const _Sentinel& __y)
> +      { return __y._M_equal(__x); }
> +    };
> +  };
> +
> +  template<typename _Range, typename _Pattern>
> +    split_view(_Range&&, _Pattern&&)
> +      -> split_view<views::all_t<_Range>, views::all_t<_Pattern>>;
> +
> +  template<forward_range _Range>
> +    split_view(_Range&&, range_value_t<_Range>)
> +      -> split_view<views::all_t<_Range>, single_view<range_value_t<_Range>>>;
> +
> +  namespace views
> +  {
> +    namespace __detail
> +    {
> +      template<typename _Range, typename _Pattern>
> +       concept __can_split_view
> +         = requires { split_view(std::declval<_Range>(), std::declval<_Pattern>()); };
> +    } // namespace __detail
> +
> +    struct _Split : __adaptor::_RangeAdaptor<_Split>
> +    {
> +      template<viewable_range _Range, typename _Pattern>
> +       requires __detail::__can_split_view<_Range, _Pattern>
> +       constexpr auto
> +       operator()(_Range&& __r, _Pattern&& __f) const
> +       {
> +         return split_view(std::forward<_Range>(__r), std::forward<_Pattern>(__f));
> +       }
> +
> +      using _RangeAdaptor<_Split>::operator();
> +      static constexpr int _S_arity = 2;
> +      template<typename _Pattern>
> +       static constexpr bool _S_has_simple_extra_args
> +         = _LazySplit::_S_has_simple_extra_args<_Pattern>;
> +    };
> +
> +    inline constexpr _Split split;
> +  } // namespace views
> +
>    namespace views
>    {
>      struct _Counted
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> index 5ef7f3f59a7..81f2a62cfaa 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> @@ -42,8 +42,6 @@ test01()
>    static_assert(__adaptor_has_simple_extra_args<decltype(views::lazy_split), char>);
>    static_assert(!__adaptor_has_simple_extra_args<decltype(views::lazy_split), std::string>);
>
> -  // Verify all adaptor closures except for views::lazy_split(pattern) have a simple
> -  // operator().
>    using views::__adaptor::__closure_has_simple_call_op;
>    __closure_has_simple_call_op auto a00 = views::all;
>    __closure_has_simple_call_op auto a01 = views::transform(std::identity{});
> @@ -57,6 +55,7 @@ test01()
>    __closure_has_simple_call_op auto a09 = views::reverse;
>    __closure_has_simple_call_op auto a10 = views::keys;
>    __closure_has_simple_call_op auto a11 = views::lazy_split(' ');
> +  __closure_has_simple_call_op auto a11a = views::split(' ');
>    // Verify composition of simple closures is simple.
>    __closure_has_simple_call_op auto b
>      = (a00 | a01) | (a02 | a03) | (a04 | a05 | a06) | (a07 | a08 | a09 | a10) | a11;
> @@ -67,6 +66,12 @@ test01()
>    static_assert(!__closure_has_simple_call_op<decltype(a12)>);
>    static_assert(!__closure_has_simple_call_op<decltype(a12 | a00)>);
>    static_assert(!__closure_has_simple_call_op<decltype(a00 | a12)>);
> +
> +  // Likewise views::split(non_view_range).
> +  auto a12a = views::split(s);
> +  static_assert(!__closure_has_simple_call_op<decltype(a12a)>);
> +  static_assert(!__closure_has_simple_call_op<decltype(a12a | a00)>);
> +  static_assert(!__closure_has_simple_call_op<decltype(a00 | a12a)>);
>  }
>
>  void
> @@ -98,6 +103,13 @@ test02()
>    auto a1 = a0 | views::all;
>    a1(x); // { dg-error "no match" }
>
> +  views::lazy_split(badarg)(x); // { dg-error "deleted function" }
> +  (views::lazy_split(badarg) | views::all)(x); // { dg-error "deleted function" }
> +  auto a0a = views::split(badarg);
> +  a0a(x); // { dg-error "no match" };
> +  auto a1a = a0a | views::all;
> +  a1a(x); // { dg-error "no match" }
> +
>    views::take(badarg)(x); // { dg-error "deleted" }
>    views::drop(badarg)(x); // { dg-error "deleted" }
>    (views::take(badarg) | views::all)(x); // { dg-error "deleted" }
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> new file mode 100644
> index 00000000000..9e6726cd07f
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/split.cc
> @@ -0,0 +1,196 @@
> +// Copyright (C) 2020-2021 Free Software Foundation, Inc.
> +//
> +// This file is part of the GNU ISO C++ Library.  This library is free
> +// software; you can redistribute it and/or modify it under the
> +// terms of the GNU General Public License as published by the
> +// Free Software Foundation; either version 3, or (at your option)
> +// any later version.
> +
> +// This library is distributed in the hope that it will be useful,
> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +// GNU General Public License for more details.
> +
> +// You should have received a copy of the GNU General Public License along
> +// with this library; see the file COPYING3.  If not see
> +// <http://www.gnu.org/licenses/>.
> +
> +// { dg-options "-std=gnu++2a" }
> +// { dg-do run { target c++2a } }
> +
> +#include <algorithm>
> +#include <ranges>
> +#include <string>
> +#include <string_view>
> +#include <testsuite_hooks.h>
> +#include <testsuite_iterators.h>
> +
> +using __gnu_test::test_range;
> +using __gnu_test::forward_iterator_wrapper;
> +using __gnu_test::input_iterator_wrapper;
> +
> +namespace ranges = std::ranges;
> +namespace views = std::ranges::views;
> +
> +using namespace std::literals;
> +
> +void
> +test01()
> +{
> +  auto from_chars = [] (auto v) {
> +    return std::stoi(std::string(v.data(), v.data() + v.size()));
> +  };
> +  auto ints = "1.2.3.4"sv
> +    | views::split('.')
> +    | views::transform(from_chars);
> +  VERIFY( ranges::equal(ints, (int[]){1,2,3,4}) );
> +}
> +
> +// The following testcases were adapted from lazy_split.cc.
> +namespace from_lazy_split_cc
> +{
> +void
> +test01()
> +{
> +  auto x = "the  quick  brown  fox"sv;
> +  auto p = std::string{"  "};
> +  auto v = x | views::split(views::all(p)); // views::all is needed here after P2281.
> +  auto i = v.begin();
> +  VERIFY( ranges::equal(*i++, "the"sv) );
> +  VERIFY( ranges::equal(*i++, "quick"sv) );
> +  VERIFY( ranges::equal(*i++, "brown"sv) );
> +  VERIFY( ranges::equal(*i++, "fox"sv) );
> +  VERIFY( i == v.end() );
> +}
> +
> +void
> +test02()
> +{
> +  auto x = "the quick brown fox"sv;
> +  auto v = x | views::split(' ');
> +  auto i = v.begin();
> +  VERIFY( ranges::equal(*i++, "the"sv) );
> +  VERIFY( ranges::equal(*i++, "quick"sv) );
> +  VERIFY( ranges::equal(*i++, "brown"sv) );
> +  VERIFY( ranges::equal(*i++, "fox"sv) );
> +  VERIFY( i == v.end() );
> +}
> +
> +void
> +test03()
> +{
> +  char x[] = "the quick brown fox";
> +  test_range<char, forward_iterator_wrapper> rx(x, x+sizeof(x)-1);
> +  auto v = rx | views::split(' ');
> +  auto i = v.begin();
> +  VERIFY( ranges::equal(*i++, "the"sv) );
> +  VERIFY( ranges::equal(*i++, "quick"sv) );
> +  VERIFY( ranges::equal(*i++, "brown"sv) );
> +  VERIFY( ranges::equal(*i++, "fox"sv) );
> +  VERIFY( i == v.end() );
> +}
> +
> +void
> +test04()
> +{
> +  auto x = "the  quick  brown  fox"sv;
> +  std::initializer_list<char> p = {' ', ' '};
> +  static_assert(!ranges::view<decltype(p)>);
> +  static_assert(std::same_as<decltype(p | views::all),
> +                            ranges::ref_view<decltype(p)>>);
> +  auto v = x | views::split(views::all(p)); // views::all is needed here after P2281.
> +  auto i = v.begin();
> +  VERIFY( ranges::equal(*i++, "the"sv) );
> +  VERIFY( ranges::equal(*i++, "quick"sv) );
> +  VERIFY( ranges::equal(*i++, "brown"sv) );
> +  VERIFY( ranges::equal(*i++, "fox"sv) );
> +  VERIFY( i == v.end() );
> +}
> +
> +void
> +test05()
> +{
> +  auto as_string = [](ranges::view auto rng) {
> +    auto in = rng | views::common;
> +    return std::string(in.begin(), in.end());
> +  };
> +  std::string str
> +    = "Now is the time for all good men to come to the aid of their county.";
> +  auto rng
> +    = str | views::split(' ') | views::transform(as_string) | views::common;
> +  std::vector<std::string> words(rng.begin(), rng.end());
> +  auto not_space_p = [](char c) { return c != ' '; };
> +  VERIFY( ranges::equal(words | views::join,
> +                       str | views::filter(not_space_p)) );
> +}
> +
> +template<auto split = views::split>
> +void
> +test06()
> +{
> +  // Verify SFINAE behavior.
> +  std::string s, p;
> +  static_assert(!requires { split(); });
> +  static_assert(!requires { split(s, p, 0); });
> +  static_assert(!requires { split(p)(); });
> +  static_assert(!requires { s | split; });
> +
> +  static_assert(!requires { s | split(p); });
> +  static_assert(!requires { split(p)(s); });
> +  static_assert(!requires { s | (split(p) | views::all); });
> +  static_assert(!requires { (split(p) | views::all)(s); });
> +
> +  static_assert(requires { s | split(views::all(p)); });
> +  static_assert(requires { split(views::all(p))(s); });
> +  static_assert(requires { s | (split(views::all(p)) | views::all); });
> +  static_assert(requires { (split(views::all(p)) | views::all)(s); });
> +
> +  auto adapt = split(p);
> +  static_assert(requires { s | adapt; });
> +  static_assert(requires { adapt(s); });
> +
> +  auto adapt2 = split(p) | views::all;
> +  static_assert(requires { s | adapt2; });
> +  static_assert(requires { adapt2(s); });
> +}
> +
> +void
> +test10()
> +{
> +  // LWG 3505
> +  auto to_string = [] (auto r) {
> +    return std::string(r.begin(), ranges::next(r.begin(), r.end()));
> +  };
> +  auto v = "xxyx"sv | views::split("xy"sv) | views::transform(to_string);
> +  VERIFY( ranges::equal(v, (std::string_view[]){"x", "x"}) );
> +}
> +
> +void
> +test11()
> +{
> +  // LWG 3478
> +  static_assert(ranges::distance(views::split("text"sv, "text"sv)) == 2);
> +  static_assert(ranges::distance(views::split(" text "sv, ' ')) == 3);
> +  static_assert(ranges::distance(views::split(" t e x t "sv, ' ')) == 6);
> +  static_assert(ranges::distance(views::split("  text  "sv, "  "sv)) == 3);
> +  static_assert(ranges::distance(views::split("  text    "sv, "  "sv)) == 4);
> +  static_assert(ranges::distance(views::split("  text     "sv, "  "sv)) == 4);
> +  static_assert(ranges::distance(views::split("t"sv, 't')) == 2);
> +  static_assert(ranges::distance(views::split("text"sv, ""sv)) == 4);
> +}
> +} // namespace from_lazy_split_cc
> +
> +int
> +main()
> +{
> +  test01();
> +
> +  from_lazy_split_cc::test01();
> +  from_lazy_split_cc::test02();
> +  from_lazy_split_cc::test03();
> +  from_lazy_split_cc::test04();
> +  from_lazy_split_cc::test05();
> +  from_lazy_split_cc::test06();
> +  from_lazy_split_cc::test10();
> +  from_lazy_split_cc::test11();
> +}
> diff --git a/libstdc++-v3/testsuite/std/ranges/p2325.cc b/libstdc++-v3/testsuite/std/ranges/p2325.cc
> index 4d075409026..d2ebe9af863 100644
> --- a/libstdc++-v3/testsuite/std/ranges/p2325.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/p2325.cc
> @@ -124,6 +124,20 @@ test08()
>    static_assert(default_initializable<type4>);
>  }
>
> +void
> +test08a()
> +{
> +  // Verify split_view is conditionally default constructible.
> +  using type1 = ranges::split_view<ranges::ref_view<int[2]>, ranges::single_view<int>>;
> +  static_assert(!default_initializable<type1>);
> +  using type2 = ranges::split_view<ranges::single_view<int>, ranges::ref_view<int[2]>>;
> +  static_assert(!default_initializable<type2>);
> +  using type3 = ranges::split_view<ranges::ref_view<int[2]>, ranges::ref_view<int[2]>>;
> +  static_assert(!default_initializable<type3>);
> +  using type4 = ranges::split_view<ranges::single_view<int>, ranges::single_view<int>>;
> +  static_assert(default_initializable<type4>);
> +}
> +
>  void
>  test09()
>  {
> diff --git a/libstdc++-v3/testsuite/std/ranges/p2367.cc b/libstdc++-v3/testsuite/std/ranges/p2367.cc
> index 5228b021602..70a0304593f 100644
> --- a/libstdc++-v3/testsuite/std/ranges/p2367.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/p2367.cc
> @@ -45,4 +45,5 @@ test01()
>
>    // Verify changes to views::lazy_split.
>    auto v6 = views::lazy_split(x, 5u);
> +  auto v7 = views::split(x, 5u);
>  }
> --
> 2.32.0.93.g670b81a890
>