创建std :: std上的范围 我正在通过“ C ++的功能编程”（是的，它的牙齿越长，但这是我现在拥有的），我正在尝试将其中的一些示例转换为C ++ 20（g ++ ...

Question

并将其转换为单个单词，降低字母，从该集合中删除任何非alphanumerics有关，然后对其进行整理。 原始写入使用了范围/v3库，我在正确转换为C ++ 20时遇到了困难。 特别是在stdin上创建范围（或视图）的初始部分，然后将其传递给下一个转换。 我正在尝试使用以下内容：

    const std::vector<std::string> words =
        // Getting a range of words (tokens) from cin
        std::views::istream<std::string>(std::cin)
        | views::transform(tolower)  // Converting all words to lower-case
        | views::transform(isalnum)  // Removing non alphanumeric characters from the words
        | views::filter([] (const std::string &s) {
                return !s.empty();
            })
        | std::ranges::sort;

this this the第一个失败，错误：

transform

在典型的C ++时尚中，这是非常精确且完全无法理解的（对我来说）。  我已经尝试创建各种方法的初始范围，但是显然它们都解决了相同的基础

main.cpp: In function ‘int main(int, char**)’:
main.cpp:38:9: error: no match for ‘operator|’ (operand types are ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’ and ‘std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int) noexcept>’)
   37 |         std::views::istream<std::string>(std::cin)
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                         |
      |                                         std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >
   38 |         | views::transform(tolower)  // Converting all words to lower-case
      |         ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
      |                           |
      |                           std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int) noexcept>
In file included from main.cpp:7:
/usr/include/c++/13/ranges:896:7: note: candidate: ‘template<class _Lhs, class _Rhs>  requires (derived_from<_Lhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) && (derived_from<_Rhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) constexpr auto std::ranges::views::__adaptor::operator|(_Lhs, _Rhs)’
  896 |       operator|(_Lhs __lhs, _Rhs __rhs)
      |       ^~~~~~~~
/usr/include/c++/13/ranges:896:7: note:   template argument deduction/substitution failed:
/usr/include/c++/13/ranges:896:7: note: constraints not satisfied
In file included from /usr/include/c++/13/compare:37,
                 from /usr/include/c++/13/bits/char_traits.h:56,
                 from /usr/include/c++/13/ios:42,
                 from /usr/include/c++/13/ostream:40,
                 from /usr/include/c++/13/iostream:41,
                 from main.cpp:1:
/usr/include/c++/13/concepts: In substitution of ‘template<class _Lhs, class _Rhs>  requires (derived_from<_Lhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) && (derived_from<_Rhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>) constexpr auto std::ranges::views::__adaptor::operator|(_Lhs, _Rhs) [with _Lhs = std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >; _Rhs = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int) noexcept>]’:
main.cpp:38:35:   required from here
/usr/include/c++/13/concepts:67:13:   required for the satisfaction of ‘derived_from<_Lhs, std::ranges::views::__adaptor::_RangeAdaptorClosure>’ [with _Lhs = std::ranges::basic_istream_view<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, char, std::char_traits<char> >]
/usr/include/c++/13/concepts:67:28: note:   ‘std::ranges::views::__adaptor::_RangeAdaptorClosure’ is not a base of ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’
   67 |     concept derived_from = __is_base_of(_Base, _Derived)
      |                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/ranges:887:7: note: candidate: ‘template<class _Self, class _Range>  requires (derived_from<typename std::remove_cvref<_Tp>::type, std::ranges::views::__adaptor::_RangeAdaptorClosure>) && (__adaptor_invocable<_Self, _Range>) constexpr auto std::ranges::views::__adaptor::operator|(_Range&&, _Self&&)’
  887 |       operator|(_Range&& __r, _Self&& __self)
      |       ^~~~~~~~
/usr/include/c++/13/ranges:887:7: note:   template argument deduction/substitution failed:
/usr/include/c++/13/ranges:887:7: note: constraints not satisfied
/usr/include/c++/13/ranges: In substitution of ‘template<class _Self, class _Range>  requires (derived_from<typename std::remove_cvref<_Tp>::type, std::ranges::views::__adaptor::_RangeAdaptorClosure>) && (__adaptor_invocable<_Self, _Range>) constexpr auto std::ranges::views::__adaptor::operator|(_Range&&, _Self&&) [with _Self = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int) noexcept>; _Range = std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >]’:
main.cpp:38:35:   required from here
/usr/include/c++/13/ranges:859:13:   required for the satisfaction of ‘__adaptor_invocable<_Self, _Range>’ [with _Self = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int)noexcept (true)>; _Range = std::ranges::basic_istream_view<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, char, std::char_traits<char> >]
/usr/include/c++/13/ranges:860:9:   in requirements  [with _Adaptor = std::ranges::views::__adaptor::_Partial<std::ranges::views::_Transform, int (*)(int)noexcept (true)>; _Args = {std::ranges::basic_istream_view<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, char, std::char_traits<char> >}]
/usr/include/c++/13/ranges:860:44: note: the required expression ‘declval<_Adaptor>()((declval<_Args>)()...)’ is invalid
  860 |       = requires { std::declval<_Adaptor>()(declval<_Args>()...); };
      |                    ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
cc1plus: note: set ‘-fconcepts-diagnostics-depth=’ to at least 2 for more detail
In file included from /usr/include/c++/13/bits/memory_resource.h:38,
                 from /usr/include/c++/13/string:58,
                 from /usr/include/c++/13/bits/locale_classes.h:40,
                 from /usr/include/c++/13/bits/ios_base.h:41,
                 from /usr/include/c++/13/ios:44:
/usr/include/c++/13/cstddef:135:3: note: candidate: ‘constexpr std::byte std::operator|(byte, byte)’
  135 |   operator|(byte __l, byte __r) noexcept
      |   ^~~~~~~~
/usr/include/c++/13/cstddef:135:18: note:   no known conversion for argument 1 from ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’ to ‘std::byte’
  135 |   operator|(byte __l, byte __r) noexcept
      |             ~~~~~^~~
/usr/include/c++/13/bits/ios_base.h:87:3: note: candidate: ‘constexpr std::_Ios_Fmtflags std::operator|(_Ios_Fmtflags, _Ios_Fmtflags)’
   87 |   operator|(_Ios_Fmtflags __a, _Ios_Fmtflags __b)
      |   ^~~~~~~~
/usr/include/c++/13/bits/ios_base.h:87:27: note:   no known conversion for argument 1 from ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’ to ‘std::_Ios_Fmtflags’
   87 |   operator|(_Ios_Fmtflags __a, _Ios_Fmtflags __b)
      |             ~~~~~~~~~~~~~~^~~
/usr/include/c++/13/bits/ios_base.h:130:3: note: candidate: ‘constexpr std::_Ios_Openmode std::operator|(_Ios_Openmode, _Ios_Openmode)’
  130 |   operator|(_Ios_Openmode __a, _Ios_Openmode __b)
      |   ^~~~~~~~
/usr/include/c++/13/bits/ios_base.h:130:27: note:   no known conversion for argument 1 from ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’ to ‘std::_Ios_Openmode’
  130 |   operator|(_Ios_Openmode __a, _Ios_Openmode __b)
      |             ~~~~~~~~~~~~~~^~~
/usr/include/c++/13/bits/ios_base.h:170:3: note: candidate: ‘constexpr std::_Ios_Iostate std::operator|(_Ios_Iostate, _Ios_Iostate)’
  170 |   operator|(_Ios_Iostate __a, _Ios_Iostate __b)
      |   ^~~~~~~~
/usr/include/c++/13/bits/ios_base.h:170:26: note:   no known conversion for argument 1 from ‘std::ranges::basic_istream_view<std::__cxx11::basic_string<char>, char, std::char_traits<char> >’ to ‘std::_Ios_Iostate’
  170 |   operator|(_Ios_Iostate __a, _Ios_Iostate __b)
      |             ~~~~~~~~~~~~~^~~

，因此结果是相同的。

明显在原始范围/V3库（带有

std::ranges::basic_istream_view

）中使用，但在当前的STD库中不起作用。

有一种方法可以使它工作吗？

我在您的代码中看到的问题：

您有

istream_range<std::string>(std::cin)

，但是这种观点不存在。

std::views::istream

Answer 1

boolean

值，而不是

弦。

管道（
1. isalnum

   ）操作员无法按照您使用的方式工作。
   

使用
2. |

   从

   std::ranges::sort：读书： std::ranges::istream_view
3. 然后对小写和字母数字过滤进行转换：std::cin将结果转化为a，然后排序：

auto words = std::ranges::istream_view<std::string>(std::cin);