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// -*- 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/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 {
// TODO(clang-15): in the Standard, it's a `constexpr bool` variable, not a concept, but constexpr variables don't
// short-circuit properly on Clang 15 (fixed in later versions), so use a concept as a workaround.
template <class _Container>
concept __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>)
_LIBCPP_NODISCARD_EXT _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>(
__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>
_LIBCPP_NODISCARD_EXT _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>)
_LIBCPP_NODISCARD_EXT _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)
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>
_LIBCPP_NODISCARD_EXT _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)
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
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