TeamHeptaMirrors/gcc
1
0
Fork 1
mirror of https://github.com/gcc-mirror/gcc.git synced 2026-05-06 14:59:39 +02:00
Code Issues Packages Projects Releases Wiki Activity

libstdc++: Implement P1739R4 changes to views::take/drop/counted

Browse Source 
This implements P1739R4 along with the resolution for LWG 3407 which
corrects the paper's wording.

libstdc++-v3/ChangeLog:

	* include/bits/ranges_util.h (views::_Drop): Forward declare.
	(subrange): Befriend views::_Drop.
	(subrange::_S_store_size): Declare constexpr instead of just
	const, remove obsolete comment.
	* include/std/ranges (views::__detail::__is_empty_view): Define.
	(views::__detail::__is_basic_string_view): Likewise.
	(views::__detail::__is_subrange): Likewise.
	(views::__detail::__is_iota_view): Likewise.
	(views::__detail::__can_take_view): Rename template parm _Tp to _Dp.
	(views::_Take): Rename template parm _Tp to _Dp, make it non-deducible
	and fix it to range_difference_t<_Range>.  Implement P1739R4 and
	LWG 3407 changes.
	(views::__detail::__can_drop_view): Rename template parm _Tp to _Dp.
	(views::_Drop): As with views::_Take.
	(views::_Counted): Implement P1739R4 changes.
	* include/std/span (__detail::__is_std_span): Rename to ...
	(__detail::__is_span): ... this and turn it into a variable
	template.
	(__detail::__is_std_array): Turn it into a variable template.
	(span::span): Adjust uses of __is_std_span and __is_std_array
	accordingly.
	* testsuite/std/ranges/adaptors/p1739.cc: New test.
This commit is contained in:
Patrick Palka
2021-10-21 11:55:16 -04:00
parent bdc42283bc
commit 9626e44713
4 changed files with 193 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
libstdc++-v3/include/bits/ranges_util.h
View File

@@ -216,6 +216,8 @@ namespace ranges
} // namespace __detail
namespace views { struct _Drop; } // defined in <ranges>
enum class subrange_kind : bool { unsized, sized };
/// The ranges::subrange class template
@@ -226,10 +228,11 @@ namespace ranges
class subrange : public view_interface<subrange<_It, _Sent, _Kind>>
{
private:
// XXX: gcc complains when using constexpr here
static const bool _S_store_size
static constexpr bool _S_store_size
= _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>;
friend struct views::_Drop; // Needs to inspect _S_store_size.
_It _M_begin = _It();
[[no_unique_address]] _Sent _M_end = _Sent();

107
libstdc++-v3/include/std/ranges
View File

@@ -42,6 +42,7 @@
#include <initializer_list>
#include <iterator>
#include <optional>
#include <span>
#include <tuple>
#include <bits/ranges_util.h>
#include <bits/refwrap.h>
@@ -2125,19 +2126,67 @@ namespace views::__adaptor
{
namespace __detail
{
template<typename _Range, typename _Tp>
template<typename _Range>
inline constexpr bool __is_empty_view = false;
template<typename _Tp>
inline constexpr bool __is_empty_view<empty_view<_Tp>> = true;
template<typename _Range>
inline constexpr bool __is_basic_string_view = false;
template<typename _CharT, typename _Traits>
inline constexpr bool __is_basic_string_view<basic_string_view<_CharT, _Traits>>
= true;
template<typename _Range>
inline constexpr bool __is_subrange = false;
template<typename _Iter, typename _Sent, subrange_kind _Kind>
inline constexpr bool __is_subrange<subrange<_Iter, _Sent, _Kind>> = true;
template<typename _Range>
inline constexpr bool __is_iota_view = false;
template<typename _Winc, typename _Bound>
inline constexpr bool __is_iota_view<iota_view<_Winc, _Bound>> = true;
template<typename _Range, typename _Dp>
concept __can_take_view
= requires { take_view(std::declval<_Range>(), std::declval<_Tp>()); };
= requires { take_view(std::declval<_Range>(), std::declval<_Dp>()); };
} // namespace __detail
struct _Take : __adaptor::_RangeAdaptor<_Take>
{
template<viewable_range _Range, typename _Tp>
requires __detail::__can_take_view<_Range, _Tp>
template<viewable_range _Range, typename _Dp = range_difference_t<_Range>>
requires __detail::__can_take_view<_Range, _Dp>
constexpr auto
operator() [[nodiscard]] (_Range&& __r, _Tp&& __n) const
operator() [[nodiscard]] (_Range&& __r, type_identity_t<_Dp> __n) const
{
return take_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
using _Tp = remove_cvref_t<_Range>;
if constexpr (__detail::__is_empty_view<_Tp>)
return _Tp();
else if constexpr (random_access_range<_Tp>
&& sized_range<_Tp>
&& (std::__detail::__is_span<_Tp>
|| __detail::__is_basic_string_view<_Tp>
|| __detail::__is_subrange<_Tp>
|| __detail::__is_iota_view<_Tp>))
{
__n = std::min<_Dp>(ranges::distance(__r), __n);
auto __begin = ranges::begin(__r);
auto __end = __begin + __n;
if constexpr (std::__detail::__is_span<_Tp>)
return span<typename _Tp::element_type>(__begin, __end);
else if constexpr (__detail::__is_basic_string_view<_Tp>)
return _Tp(__begin, __end);
else if constexpr (__detail::__is_subrange<_Tp>)
return subrange<iterator_t<_Tp>>(__begin, __end);
else
return iota_view(*__begin, *__end);
}
else
return take_view(std::forward<_Range>(__r), __n);
}
using _RangeAdaptor<_Take>::operator();
@@ -2372,19 +2421,49 @@ namespace views::__adaptor
{
namespace __detail
{
template<typename _Range, typename _Tp>
template<typename _Range, typename _Dp>
concept __can_drop_view
= requires { drop_view(std::declval<_Range>(), std::declval<_Tp>()); };
= requires { drop_view(std::declval<_Range>(), std::declval<_Dp>()); };
} // namespace __detail
struct _Drop : __adaptor::_RangeAdaptor<_Drop>
{
template<viewable_range _Range, typename _Tp>
requires __detail::__can_drop_view<_Range, _Tp>
template<viewable_range _Range, typename _Dp = range_difference_t<_Range>>
requires __detail::__can_drop_view<_Range, _Dp>
constexpr auto
operator() [[nodiscard]] (_Range&& __r, _Tp&& __n) const
operator() [[nodiscard]] (_Range&& __r, type_identity_t<_Dp> __n) const
{
return drop_view(std::forward<_Range>(__r), std::forward<_Tp>(__n));
using _Tp = remove_cvref_t<_Range>;
if constexpr (__detail::__is_empty_view<_Tp>)
return _Tp();
else if constexpr (random_access_range<_Tp>
&& sized_range<_Tp>
&& (std::__detail::__is_span<_Tp>
|| __detail::__is_basic_string_view<_Tp>
|| __detail::__is_iota_view<_Tp>
|| __detail::__is_subrange<_Tp>))
{
__n = std::min<_Dp>(ranges::distance(__r), __n);
auto __begin = ranges::begin(__r) + __n;
auto __end = ranges::end(__r);
if constexpr (std::__detail::__is_span<_Tp>)
return span<typename _Tp::element_type>(__begin, __end);
else if constexpr (__detail::__is_subrange<_Tp>)
{
if constexpr (_Tp::_S_store_size)
{
using ranges::__detail::__to_unsigned_like;
auto __m = ranges::distance(__r) - __n;
return _Tp(__begin, __end, __to_unsigned_like(__m));
}
else
return _Tp(__begin, __end);
}
else
return _Tp(__begin, __end);
}
else
return drop_view(std::forward<_Range>(__r), __n);
}
using _RangeAdaptor<_Drop>::operator();
@@ -3519,7 +3598,9 @@ namespace views::__adaptor
constexpr auto
operator() [[nodiscard]] (_Iter __i, iter_difference_t<_Iter> __n) const
{
if constexpr (random_access_iterator<_Iter>)
if constexpr (contiguous_iterator<_Iter>)
return span(std::__to_address(__i), __n);
else if constexpr (random_access_iterator<_Iter>)
return subrange(__i, __i + __n);
else
return subrange(counted_iterator(std::move(__i), __n),

12
libstdc++-v3/include/std/span
View File

@@ -58,16 +58,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __detail
{
template<typename _Tp>
struct __is_std_span : false_type { };
inline constexpr bool __is_span = false;
template<typename _Tp, size_t _Num>
struct __is_std_span<span<_Tp, _Num>> : true_type { };
inline constexpr bool __is_span<span<_Tp, _Num>> = true;
template<typename _Tp>
struct __is_std_array : false_type { };
inline constexpr bool __is_std_array = false;
template<typename _Tp, size_t _Num>
struct __is_std_array<std::array<_Tp, _Num>> : true_type { };
inline constexpr bool __is_std_array<std::array<_Tp, _Num>> = true;
template<size_t _Extent>
class __extent_storage
@@ -203,8 +203,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Range>
requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
&& (ranges::borrowed_range<_Range> || is_const_v<element_type>)
&& (!__detail::__is_std_span<remove_cvref_t<_Range>>::value)
&& (!__detail::__is_std_array<remove_cvref_t<_Range>>::value)
&& (!__detail::__is_span<remove_cvref_t<_Range>>)
&& (!__detail::__is_std_array<remove_cvref_t<_Range>>)
&& (!is_array_v<remove_cvref_t<_Range>>)
&& __is_compatible_ref<ranges::range_reference_t<_Range>>::value
constexpr explicit(extent != dynamic_extent)

88
libstdc++-v3/testsuite/std/ranges/adaptors/p1739.cc Normal file
View File

@@ -0,0 +1,88 @@
// { dg-options "-std=gnu++20" }
// { dg-do run { target c++20 } }
#include <algorithm>
#include <ranges>
#include <testsuite_hooks.h>
// Verify P1739R4 (and LWG 3407) changes to views::take/drop/counted.
namespace ranges = std::ranges;
namespace views = ranges::views;
void
test01()
{
ranges::empty_view<int> v;
using ty = decltype(v);
using ty = decltype(views::take(v, 42));
using ty = decltype(views::drop(v, 42));
}
void
test02()
{
int x[] = {1,2,3,4,5};
std::span r(x, x+5);
using ty = decltype(r);
std::same_as<ty> auto v1 = views::take(r, 2);
VERIFY( ranges::equal(v1, (int[]){1,2}) );
std::same_as<ty> auto v2 = views::drop(r, 3);
VERIFY( ranges::equal(v2, (int[]){4,5}) );
std::same_as<ty> auto v3 = views::counted(r.begin(), 4);
VERIFY( ranges::equal(v3, (int[]){1,2,3,4}) );
}
void
test03()
{
using namespace std::literals;
std::string_view r = "hello world"sv;
using ty = decltype(r);
std::same_as<ty> auto v1 = views::take(r, 5);
VERIFY( ranges::equal(v1, "hello"sv) );
std::same_as<ty> auto v2 = views::drop(r, 6);
VERIFY( ranges::equal(v2, "world"sv) );
}
void
test04()
{
int x[] = {1,2,3,4,5};
ranges::subrange r(x, x+5);
using ty = decltype(r);
std::same_as<ty> auto v1 = views::take(r, 2);
VERIFY( ranges::equal(v1, (int[]){1,2}) );
std::same_as<ty> auto v2 = views::drop(r, 1);
VERIFY( ranges::equal(v2, (int[]){2,3,4,5}) );
}
void
test05()
{
auto r1 = views::iota(1, 6);
using ty1 = decltype(r1);
std::same_as<ty1> auto v1 = views::take(r1, 2);
VERIFY( ranges::equal(v1, (int[]){1,2}) );
std::same_as<ty1> auto v2 = views::drop(r1, 3);
VERIFY( ranges::equal(v2, (int[]){4,5}) );
}
int
main()
{
test01();
test02();
test03();
test04();
test05();
}