include/__ranges/to.h - llvm-project/libcxx - Git at Google

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #ifndef _LIBCPP___RANGES_TO_H
 #define _LIBCPP___RANGES_TO_H

 #include <__algorithm/ranges_copy.h>
 #include <__concepts/constructible.h>
 #include <__concepts/convertible_to.h>
 #include <__concepts/derived_from.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__functional/bind_back.h>
 #include <__iterator/back_insert_iterator.h>
 #include <__iterator/insert_iterator.h>
 #include <__iterator/iterator_traits.h>
 #include <__ranges/access.h>
 #include <__ranges/concepts.h>
 #include <__ranges/from_range.h>
 #include <__ranges/range_adaptor.h>
 #include <__ranges/ref_view.h>
 #include <__ranges/size.h>
 #include <__ranges/transform_view.h>
 #include <__type_traits/add_pointer.h>
 #include <__type_traits/is_const.h>
 #include <__type_traits/is_volatile.h>
 #include <__type_traits/type_identity.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
 #include <cstddef>

 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif

 _LIBCPP_BEGIN_NAMESPACE_STD

 #if _LIBCPP_STD_VER >= 23

 namespace ranges {

 template <class _Container>
 constexpr bool __reservable_container =
     sized_range<_Container> && requires(_Container& __c, range_size_t<_Container> __n) {
       __c.reserve(__n);
       { __c.capacity() } -> same_as<decltype(__n)>;
       { __c.max_size() } -> same_as<decltype(__n)>;
     };

 template <class _Container, class _Ref>
 constexpr bool __container_insertable = requires(_Container& __c, _Ref&& __ref) {
   requires(
       requires { __c.push_back(std::forward<_Ref>(__ref)); } ||
       requires { __c.insert(__c.end(), std::forward<_Ref>(__ref)); });
 };

 template <class _Ref, class _Container>
 _LIBCPP_HIDE_FROM_ABI constexpr auto __container_inserter(_Container& __c) {
   if constexpr (requires { __c.push_back(std::declval<_Ref>()); }) {
     return std::back_inserter(__c);
   } else {
     return std::inserter(__c, __c.end());
   }
 }

 // Note: making this a concept allows short-circuiting the second condition.
 template <class _Container, class _Range>
 concept __try_non_recursive_conversion =
     !input_range<_Container> || convertible_to<range_reference_t<_Range>, range_value_t<_Container>>;

 template <class _Container, class _Range, class... _Args>
 concept __constructible_from_iter_pair =
     common_range<_Range> && requires { typename iterator_traits<iterator_t<_Range>>::iterator_category; } &&
     derived_from<typename iterator_traits<iterator_t<_Range>>::iterator_category, input_iterator_tag> &&
     constructible_from<_Container, iterator_t<_Range>, sentinel_t<_Range>, _Args...>;

 template <class>
 concept __always_false = false;

 // `ranges::to` base template -- the `_Container` type is a simple type template parameter.
 template <class _Container, input_range _Range, class... _Args>
   requires(!view<_Container>)
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Container to(_Range&& __range, _Args&&... __args) {
   // Mandates: C is a cv-unqualified class type.
   static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
   static_assert(
       !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");

   // First see if the non-recursive case applies -- the conversion target is either:
   // - a range with a convertible value type;
   // - a non-range type which might support being created from the input argument(s) (e.g. an `optional`).
   if constexpr (__try_non_recursive_conversion<_Container, _Range>) {
     // Case 1 -- construct directly from the given range.
     if constexpr (constructible_from<_Container, _Range, _Args...>) {
       return _Container(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
     }

     // Case 2 -- construct using the `from_range_t` tagged constructor.
     else if constexpr (constructible_from<_Container, from_range_t, _Range, _Args...>) {
       return _Container(from_range, std::forward<_Range>(__range), std::forward<_Args>(__args)...);
     }

     // Case 3 -- construct from a begin-end iterator pair.
     else if constexpr (__constructible_from_iter_pair<_Container, _Range, _Args...>) {
       return _Container(ranges::begin(__range), ranges::end(__range), std::forward<_Args>(__args)...);
     }

     // Case 4 -- default-construct (or construct from the extra arguments) and insert, reserving the size if possible.
     else if constexpr (constructible_from<_Container, _Args...> &&
                        __container_insertable<_Container, range_reference_t<_Range>>) {
       _Container __result(std::forward<_Args>(__args)...);
       if constexpr (sized_range<_Range> && __reservable_container<_Container>) {
         __result.reserve(static_cast<range_size_t<_Container>>(ranges::size(__range)));
       }

       ranges::copy(__range, ranges::__container_inserter<range_reference_t<_Range>>(__result));

       return __result;

     } else {
       static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
     }

     // Try the recursive case.
   } else if constexpr (input_range<range_reference_t<_Range>>) {
     return ranges::to<_Container>(
         ref_view(__range) | views::transform([](auto&& __elem) {
           return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
         }),
         std::forward<_Args>(__args)...);

   } else {
     static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
   }
 }

 template <class _Range>
 struct __minimal_input_iterator {
   using iterator_category = input_iterator_tag;
   using value_type        = range_value_t<_Range>;
   using difference_type   = ptrdiff_t;
   using pointer           = add_pointer_t<range_reference_t<_Range>>;
   using reference         = range_reference_t<_Range>;

   reference operator*() const;
   pointer operator->() const;
   __minimal_input_iterator& operator++();
   __minimal_input_iterator operator++(int);
   bool operator==(const __minimal_input_iterator&) const;
 };

 // Deduces the full type of the container from the given template template parameter.
 template <template <class...> class _Container, input_range _Range, class... _Args>
 struct _Deducer {
   _LIBCPP_HIDE_FROM_ABI static constexpr auto __deduce_func() {
     using _InputIter = __minimal_input_iterator<_Range>;

     // Case 1 -- can construct directly from the given range.
     if constexpr (requires { _Container(std::declval<_Range>(), std::declval<_Args>()...); }) {
       using _Result = decltype( //
           _Container(std::declval<_Range>(), std::declval<_Args>()...));
       return type_identity<_Result>{};

       // Case 2 -- can construct from the given range using the `from_range_t` tagged constructor.
     } else if constexpr ( //
         requires { _Container(from_range, std::declval<_Range>(), std::declval<_Args>()...); }) {
       using _Result = //
           decltype(_Container(from_range, std::declval<_Range>(), std::declval<_Args>()...));
       return type_identity<_Result>{};

       // Case 3 -- can construct from a begin-end iterator pair.
     } else if constexpr ( //
         requires { _Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...); }) {
       using _Result =
           decltype(_Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...));
       return type_identity<_Result>{};

     } else {
       static_assert(__always_false<_Range>,
                     "ranges::to: unable to deduce the container type from the template template argument.");
     }
   }

   using type = typename decltype(__deduce_func())::type;
 };

 // `ranges::to` specialization -- `_Container` is a template template parameter requiring deduction to figure out the
 // container element type.
 template <template <class...> class _Container, input_range _Range, class... _Args>
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Range&& __range, _Args&&... __args) {
   using _DeduceExpr = typename _Deducer<_Container, _Range, _Args...>::type;
   return ranges::to<_DeduceExpr>(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
 }

 // Range adaptor closure object 1 -- wrapping the `ranges::to` version where `_Container` is a simple type template
 // parameter.
 template <class _Container, class... _Args>
   requires(!view<_Container>)
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
   // Mandates: C is a cv-unqualified class type.
   static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
   static_assert(
       !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");

   auto __to_func = []<input_range _Range, class... _Tail>(_Range&& __range, _Tail&&... __tail) static
     requires requires { //
       /**/ ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
     }
   { return ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...); };

   return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
 }

 // Range adaptor closure object 2 -- wrapping the `ranges::to` version where `_Container` is a template template
 // parameter.
 template <template <class...> class _Container, class... _Args>
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
   // clang-format off
   auto __to_func = []<input_range _Range, class... _Tail,
                       class _DeducedExpr = typename _Deducer<_Container, _Range, _Tail...>::type>
     (_Range&& __range, _Tail&& ... __tail) static
       requires requires { //
       /**/ ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
     }
   {
     return ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
   };
   // clang-format on

   return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
 }

 } // namespace ranges

 #endif // _LIBCPP_STD_VER >= 23

 _LIBCPP_END_NAMESPACE_STD

 #endif // _LIBCPP___RANGES_TO_H
	// -- C++ --
	//===----------------------------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#ifndef _LIBCPP___RANGES_TO_H
	#define _LIBCPP___RANGES_TO_H

	#include <__algorithm/ranges_copy.h>
	#include <__concepts/constructible.h>
	#include <__concepts/convertible_to.h>
	#include <__concepts/derived_from.h>
	#include <__concepts/same_as.h>
	#include <__config>
	#include <__functional/bind_back.h>
	#include <__iterator/back_insert_iterator.h>
	#include <__iterator/insert_iterator.h>
	#include <__iterator/iterator_traits.h>
	#include <__ranges/access.h>
	#include <__ranges/concepts.h>
	#include <__ranges/from_range.h>
	#include <__ranges/range_adaptor.h>
	#include <__ranges/ref_view.h>
	#include <__ranges/size.h>
	#include <__ranges/transform_view.h>
	#include <__type_traits/add_pointer.h>
	#include <__type_traits/is_const.h>
	#include <__type_traits/is_volatile.h>
	#include <__type_traits/type_identity.h>
	#include <__utility/declval.h>
	#include <__utility/forward.h>
	#include <cstddef>

	#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
	# pragma GCC system_header
	#endif

	_LIBCPP_BEGIN_NAMESPACE_STD

	#if _LIBCPP_STD_VER >= 23

	namespace ranges {

	template <class _Container>
	constexpr bool __reservable_container =
	sized_range<_Container> && requires(_Container& __c, range_size_t<_Container> __n) {
	__c.reserve(__n);
	{ __c.capacity() } -> same_as<decltype(__n)>;
	{ __c.max_size() } -> same_as<decltype(__n)>;
	};

	template <class _Container, class _Ref>
	constexpr bool __container_insertable = requires(_Container& __c, _Ref&& __ref) {
	requires(
	requires { __c.push_back(std::forward<_Ref>(__ref)); } \|\|
	requires { __c.insert(__c.end(), std::forward<_Ref>(__ref)); });
	};

	template <class _Ref, class _Container>
	_LIBCPP_HIDE_FROM_ABI constexpr auto __container_inserter(_Container& __c) {
	if constexpr (requires { __c.push_back(std::declval<_Ref>()); }) {
	return std::back_inserter(__c);
	} else {
	return std::inserter(__c, __c.end());
	}
	}

	// Note: making this a concept allows short-circuiting the second condition.
	template <class _Container, class _Range>
	concept __try_non_recursive_conversion =
	!input_range<_Container> \|\| convertible_to<range_reference_t<_Range>, range_value_t<_Container>>;

	template <class _Container, class _Range, class... _Args>
	concept __constructible_from_iter_pair =
	common_range<_Range> && requires { typename iterator_traits<iterator_t<_Range>>::iterator_category; } &&
	derived_from<typename iterator_traits<iterator_t<_Range>>::iterator_category, input_iterator_tag> &&
	constructible_from<_Container, iterator_t<_Range>, sentinel_t<_Range>, _Args...>;

	template <class>
	concept __always_false = false;

	// `ranges::to` base template -- the `_Container` type is a simple type template parameter.
	template <class _Container, input_range _Range, class... _Args>
	requires(!view<_Container>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Container to(_Range&& __range, _Args&&... __args) {
	// Mandates: C is a cv-unqualified class type.
	static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
	static_assert(
	!is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");

	// First see if the non-recursive case applies -- the conversion target is either:
	// - a range with a convertible value type;
	// - a non-range type which might support being created from the input argument(s) (e.g. an `optional`).
	if constexpr (__try_non_recursive_conversion<_Container, _Range>) {
	// Case 1 -- construct directly from the given range.
	if constexpr (constructible_from<_Container, _Range, _Args...>) {
	return _Container(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
	}

	// Case 2 -- construct using the `from_range_t` tagged constructor.
	else if constexpr (constructible_from<_Container, from_range_t, _Range, _Args...>) {
	return _Container(from_range, std::forward<_Range>(__range), std::forward<_Args>(__args)...);
	}

	// Case 3 -- construct from a begin-end iterator pair.
	else if constexpr (__constructible_from_iter_pair<_Container, _Range, _Args...>) {
	return _Container(ranges::begin(__range), ranges::end(__range), std::forward<_Args>(__args)...);
	}

	// Case 4 -- default-construct (or construct from the extra arguments) and insert, reserving the size if possible.
	else if constexpr (constructible_from<_Container, _Args...> &&
	__container_insertable<_Container, range_reference_t<_Range>>) {
	_Container __result(std::forward<_Args>(__args)...);
	if constexpr (sized_range<_Range> && __reservable_container<_Container>) {
	__result.reserve(static_cast<range_size_t<_Container>>(ranges::size(__range)));
	}

	ranges::copy(__range, ranges::__container_inserter<range_reference_t<_Range>>(__result));

	return __result;

	} else {
	static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
	}

	// Try the recursive case.
	} else if constexpr (input_range<range_reference_t<_Range>>) {
	return ranges::to<_Container>(
	ref_view(__range) \| views::transform([](auto&& __elem) {
	return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
	}),
	std::forward<_Args>(__args)...);

	} else {
	static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
	}
	}

	template <class _Range>
	struct __minimal_input_iterator {
	using iterator_category = input_iterator_tag;
	using value_type = range_value_t<_Range>;
	using difference_type = ptrdiff_t;
	using pointer = add_pointer_t<range_reference_t<_Range>>;
	using reference = range_reference_t<_Range>;

	reference operator*() const;
	pointer operator->() const;
	__minimal_input_iterator& operator++();
	__minimal_input_iterator operator++(int);
	bool operator==(const __minimal_input_iterator&) const;
	};

	// Deduces the full type of the container from the given template template parameter.
	template <template <class...> class _Container, input_range _Range, class... _Args>
	struct _Deducer {
	_LIBCPP_HIDE_FROM_ABI static constexpr auto __deduce_func() {
	using _InputIter = __minimal_input_iterator<_Range>;

	// Case 1 -- can construct directly from the given range.
	if constexpr (requires { _Container(std::declval<_Range>(), std::declval<_Args>()...); }) {
	using _Result = decltype( //
	_Container(std::declval<_Range>(), std::declval<_Args>()...));
	return type_identity<_Result>{};

	// Case 2 -- can construct from the given range using the `from_range_t` tagged constructor.
	} else if constexpr ( //
	requires { _Container(from_range, std::declval<_Range>(), std::declval<_Args>()...); }) {
	using _Result = //
	decltype(_Container(from_range, std::declval<_Range>(), std::declval<_Args>()...));
	return type_identity<_Result>{};

	// Case 3 -- can construct from a begin-end iterator pair.
	} else if constexpr ( //
	requires { _Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...); }) {
	using _Result =
	decltype(_Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...));
	return type_identity<_Result>{};

	} else {
	static_assert(__always_false<_Range>,
	"ranges::to: unable to deduce the container type from the template template argument.");
	}
	}

	using type = typename decltype(__deduce_func())::type;
	};

	// `ranges::to` specialization -- `_Container` is a template template parameter requiring deduction to figure out the
	// container element type.
	template <template <class...> class _Container, input_range _Range, class... _Args>
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Range&& __range, _Args&&... __args) {
	using _DeduceExpr = typename _Deducer<_Container, _Range, _Args...>::type;
	return ranges::to<_DeduceExpr>(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
	}

	// Range adaptor closure object 1 -- wrapping the `ranges::to` version where `_Container` is a simple type template
	// parameter.
	template <class _Container, class... _Args>
	requires(!view<_Container>)
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
	// Mandates: C is a cv-unqualified class type.
	static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
	static_assert(
	!is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");

	auto __to_func = []<input_range _Range, class... _Tail>(_Range&& __range, _Tail&&... __tail) static
	requires requires { //
	/**/ ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
	}
	{ return ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...); };

	return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
	}

	// Range adaptor closure object 2 -- wrapping the `ranges::to` version where `_Container` is a template template
	// parameter.
	template <template <class...> class _Container, class... _Args>
	[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
	// clang-format off
	auto __to_func = []<input_range _Range, class... _Tail,
	class _DeducedExpr = typename _Deducer<_Container, _Range, _Tail...>::type>
	(_Range&& __range, _Tail&& ... __tail) static
	requires requires { //
	/**/ ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
	}
	{
	return ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
	};
	// clang-format on

	return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
	}

	} // namespace ranges

	#endif // _LIBCPP_STD_VER >= 23

	_LIBCPP_END_NAMESPACE_STD

	#endif // _LIBCPP___RANGES_TO_H