view::c_str是否存在视图问题：：拆分？

Question

给定的

auto cstr = "quick brown fox";

我们有一组适配器，只用于拆分单词，然后尝试将它们显示为格式化范围。

auto adaptors = ranges::view::split(' ') | ranges::view::all;

如果源是string_view，则可以。

auto sv = std::string_view{cstr};
ranges::copy(sv | adaptors, ranges::ostream_iterator(std::cout,";") );

输出：[魔盒]

[q,u,i,c,k];[b,r,o,w,n];[f,o,x];

然后尝试使用view::c_str

auto cstr_rng = ranges::view::c_str(cstr);
// Won't compile
// ranges::copy(cstr_rng | adaptors, ranges::ostream_iterator(std::cout,";") );

错误：[行政长官]

/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/view/split.hpp: In instantiation of 'ranges::v3::split_view<Rng, Fun>::cursor<IsConst>::cursor(ranges::v3::split_view<Rng, Fun>::cursor<IsConst>::fun_ref_t, ranges::v3::iterator_t<Rng>, ranges::v3::sentinel_t<Rng>) [with bool IsConst = true; Rng = ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>; Fun = ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&>; ranges::v3::split_view<Rng, Fun>::cursor<IsConst>::fun_ref_t = ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&>; ranges::v3::iterator_t<Rng> = ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::adaptor_cursor<const char*, ranges::v3::adaptor_base> >; ranges::v3::sentinel_t<Rng> = ranges::v3::adaptor_sentinel<ranges::v3::unreachable, ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>::sentinel_adaptor>]':
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/view/split.hpp:128:69:   required from 'ranges::v3::split_view<Rng, Fun>::cursor<true> ranges::v3::split_view<Rng, Fun>::begin_cursor() const [with int _concept_requires_125 = 42; typename std::enable_if<((_concept_requires_125 == 43) || (ranges::v3::concepts::models<ranges::v3::concepts::Invocable, const Fun&, decltype (ranges::v3::function_objects::begin(declval<T&>())), decltype (ranges::v3::function_objects::end(declval<Rng&>()))>() && ranges::v3::concepts::models<ranges::v3::concepts::Range, const D>())), int>::type <anonymous> = 0; Rng = ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>; Fun = ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&>]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/range_access.hpp:176:13:   required from 'static constexpr decltype (static_cast<const Rng&>(rng).begin_cursor()) ranges::v3::range_access::begin_cursor(Rng&, int) [with Rng = const ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; decltype (static_cast<const Rng&>(rng).begin_cursor()) = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true>]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/view_facade.hpp:93:51:   required from 'ranges::v3::detail::facade_iterator_t<const D> ranges::v3::view_facade<Derived, C>::begin() const [with D = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; int _concept_requires_90 = 42; typename std::enable_if<((_concept_requires_113 == 43) || typename ranges::v3::concepts::Same::same<C, Cur>::type()), int>::type <anonymous> = 0; Derived = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; ranges::v3::cardinality Cardinality = (ranges::v3::cardinality)-1; ranges::v3::detail::facade_iterator_t<const D> = ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true> >; typename std::decay<decltype (ranges::v3::range_access::begin_cursor(declval<const D&>(), 42))>::type = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true>]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/begin_end.hpp:58:17:   required from 'static constexpr I ranges::v3::_begin_::fn::impl_(R&, int) [with R = const ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; I = ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true> >; int _concept_requires_56 = 42; typename std::enable_if<((_concept_requires_56 == 43) || ranges::v3::concepts::models<ranges::v3::concepts::Iterator, I>()), int>::type <anonymous> = 0]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/begin_end.hpp:76:17:   required from 'constexpr decltype (ranges::v3::_begin_::fn::impl_(r, 42)) ranges::v3::_begin_::fn::operator()(R&) const [with R = const ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; decltype (ranges::v3::_begin_::fn::impl_(r, 42)) = ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true> >]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/begin_end.hpp:145:56:   [ skipping 6 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/utility/functional.hpp:718:13:   required by substitution of 'template<class Arg, class Pipe> static decltype (pipe(static_cast<Arg&&>(arg))) ranges::v3::pipeable<ranges::v3::view::all_fn>::pipe<Arg, Pipe>(Arg&&, Pipe) [with Arg = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; Pipe = ranges::v3::view::all_fn]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/utility/functional.hpp:728:9:   required by substitution of 'template<class Arg, class Pipe, int _concept_requires_726, typename std::enable_if<((_concept_requires_726 == 43) || ((! ranges::v3::is_pipeable<T>()) && ranges::v3::is_pipeable<Pipe>())), int>::type <anonymous> > decltype (ranges::v3::pipeable_access::impl<Pipe>::pipe(static_cast<Arg&&>(arg), pipe)) ranges::v3::operator|(Arg&&, Pipe) [with Arg = ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >; Pipe = ranges::v3::view::all_fn; int _concept_requires_726 = 42; typename std::enable_if<((_concept_requires_726 == 43) || ((! ranges::v3::is_pipeable<T>()) && ranges::v3::is_pipeable<Pipe>())), int>::type <anonymous> = 0]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/utility/functional.hpp:644:17:   required by substitution of 'template<class Arg> decltype (((static_cast<Arg&&>(arg) | ((const ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn>*)this)->ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn>::pipe0_) | ((const ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn>*)this)->ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn>::pipe1_)) ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn>::operator()<Arg>(Arg&&) const [with Arg = ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/utility/functional.hpp:718:13:   required by substitution of 'template<class Arg, class Pipe> static decltype (pipe(static_cast<Arg&&>(arg))) ranges::v3::pipeable<ranges::v3::detail::pipeable_binder<ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn> > >::pipe<Arg, Pipe>(Arg&&, Pipe) [with Arg = ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&; Pipe = ranges::v3::detail::pipeable_binder<ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn> >]'
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/utility/functional.hpp:728:9:   required by substitution of 'template<class Arg, class Pipe, int _concept_requires_726, typename std::enable_if<((_concept_requires_726 == 43) || ((! ranges::v3::is_pipeable<T>()) && ranges::v3::is_pipeable<Pipe>())), int>::type <anonymous> > decltype (ranges::v3::pipeable_access::impl<Pipe>::pipe(static_cast<Arg&&>(arg), pipe)) ranges::v3::operator|(Arg&&, Pipe) [with Arg = ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&; Pipe = ranges::v3::detail::pipeable_binder<ranges::v3::detail::composed_pipe<ranges::v3::view::view<ranges::v3::detail::pipeable_binder<std::_Bind<ranges::v3::view::split_fn(std::_Placeholder<1>, char)> > >, ranges::v3::view::all_fn> >; int _concept_requires_726 = 42; typename std::enable_if<((_concept_requires_726 == 43) || ((! ranges::v3::is_pipeable<T>()) && ranges::v3::is_pipeable<Pipe>())), int>::type <anonymous> = 0]'
<source>:20:29:   required from here
/opt/compiler-explorer/libs/rangesv3/trunk/include/range/v3/view/split.hpp:114:36: error: no match for call to '(const ranges::v3::invoke_fn) (ranges::v3::split_view<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>, ranges::v3::view::split_fn::element_pred<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char>&> >::cursor<true>::fun_ref_t&, ranges::v3::iterator_t<ranges::v3::delimit_view<ranges::v3::iterator_range<const char*, ranges::v3::unreachable>, char> >&, ranges::v3::_basic_iterator_::basic_iterator<ranges::v3::adaptor_cursor<const char*, ranges::v3::adaptor_base> >)'
                     auto p = invoke(fun, first, ranges::next(first));
                          ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

这是view::c_str的某种限制，还是view::c_str与视图之间存在一些问题：：拆分？

/g/bTK4Yp

wandbox.org/permlink/ZkDmSkBxPg80oebS

Answer 1

此错误是由于split_view中的一个错误造成的。具体来说，在split_view::cursor::cursor()中

cursor(fun_ref_t fun, iterator_t<Rng> first, sentinel_t<Rng> last)
    : cur_(first), last_(last), fun_(fun)
{
    // For skipping an initial zero-length match
    auto p = invoke(fun, first, ranges::next(first)); // <----
    zero_ = p.first && first == p.second;
}

标记行使用来自基础范围的两个迭代器调用fun，尽管第150-199行上的谓词函数实现接受一个迭代器，并从底层范围接收哨兵。

20180228最新情况：

这个补丁是签入的，这个bug不应该再在range-v3主版上重现。