libstdc++: Implement P2474R2 changes to views::take/drop
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Commit Message
Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
libstdc++-v3/ChangeLog:
* include/std/ranges (views::__detail::__is_repeat_view): Define
and later define a partial specialization.
(views::__detail::__take_of_repeat_view): Declare and later define.
(views::__detail::__drop_of_repeat_view): Likewise.
(views::_Take::operator()): Return a repeat_view if the argument
is a repeat_view as per P2474R2.
(views::_Drop::operator()): Likewise.
(repeat_view): Befriend __take/drop_of_repeat_view.
* testsuite/std/ranges/repeat/1.cc (test04): New test.
---
libstdc++-v3/include/std/ranges | 56 +++++++++++++++++++
libstdc++-v3/testsuite/std/ranges/repeat/1.cc | 33 +++++++++++
2 files changed, 89 insertions(+)
Comments
On Wed, 19 Oct 2022, 17:47 Patrick Palka via Libstdc++, <
libstdc++@gcc.gnu.org> wrote:
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
>
OK
> libstdc++-v3/ChangeLog:
>
> * include/std/ranges (views::__detail::__is_repeat_view): Define
> and later define a partial specialization.
> (views::__detail::__take_of_repeat_view): Declare and later define.
> (views::__detail::__drop_of_repeat_view): Likewise.
> (views::_Take::operator()): Return a repeat_view if the argument
> is a repeat_view as per P2474R2.
> (views::_Drop::operator()): Likewise.
> (repeat_view): Befriend __take/drop_of_repeat_view.
> * testsuite/std/ranges/repeat/1.cc (test04): New test.
> ---
> libstdc++-v3/include/std/ranges | 56 +++++++++++++++++++
> libstdc++-v3/testsuite/std/ranges/repeat/1.cc | 33 +++++++++++
> 2 files changed, 89 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/ranges
> b/libstdc++-v3/include/std/ranges
> index b29264931cc..6de08244bd1 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -2257,6 +2257,13 @@ namespace views::__adaptor
> template<typename _Winc, typename _Bound>
> inline constexpr bool __is_iota_view<iota_view<_Winc, _Bound>> =
> true;
>
> + template<typename _Range>
> + inline constexpr bool __is_repeat_view = false;
> +
> + template<typename _Range>
> + constexpr auto
> + __take_of_repeat_view(_Range&&, range_difference_t<_Range>); //
> defined later
> +
> template<typename _Range, typename _Dp>
> concept __can_take_view
> = requires { take_view(std::declval<_Range>(),
> std::declval<_Dp>()); };
> @@ -2291,6 +2298,8 @@ namespace views::__adaptor
> else
> return iota_view(*__begin, *__end);
> }
> + else if constexpr (__detail::__is_repeat_view<_Tp>)
> + return
> __detail::__take_of_repeat_view(std::forward<_Range>(__r), __n);
> else
> return take_view(std::forward<_Range>(__r), __n);
> }
> @@ -2527,6 +2536,10 @@ namespace views::__adaptor
> {
> namespace __detail
> {
> + template<typename _Range>
> + constexpr auto
> + __drop_of_repeat_view(_Range&&, range_difference_t<_Range>); //
> defined later
> +
> template<typename _Range, typename _Dp>
> concept __can_drop_view
> = requires { drop_view(std::declval<_Range>(),
> std::declval<_Dp>()); };
> @@ -2568,6 +2581,8 @@ namespace views::__adaptor
> else
> return _Tp(__begin, __end);
> }
> + else if constexpr (__detail::__is_repeat_view<_Tp>)
> + return
> __detail::__drop_of_repeat_view(std::forward<_Range>(__r), __n);
> else
> return drop_view(std::forward<_Range>(__r), __n);
> }
> @@ -7367,6 +7382,14 @@ namespace views::__adaptor
>
> struct _Iterator;
>
> + template<typename _Range>
> + friend constexpr auto
> + views::__detail::__take_of_repeat_view(_Range&&,
> range_difference_t<_Range>);
> +
> + template<typename _Range>
> + friend constexpr auto
> + views::__detail::__drop_of_repeat_view(_Range&&,
> range_difference_t<_Range>);
> +
> public:
> repeat_view() requires default_initializable<_Tp> = default;
>
> @@ -7540,6 +7563,9 @@ namespace views::__adaptor
> {
> namespace __detail
> {
> + template<typename _Tp, typename _Bound>
> + inline constexpr bool __is_repeat_view<repeat_view<_Tp, _Bound>> =
> true;
> +
> template<typename _Tp>
> concept __can_repeat_view
> = requires { repeat_view(std::declval<_Tp>()); };
> @@ -7565,6 +7591,36 @@ namespace views::__adaptor
> };
>
> inline constexpr _Repeat repeat;
> +
> + namespace __detail
> + {
> + template<typename _Range>
> + constexpr auto
> + __take_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n)
> + {
> + using _Tp = remove_cvref_t<_Range>;
> + static_assert(__is_repeat_view<_Tp>);
> + if constexpr (sized_range<_Tp>)
> + return views::repeat(*__r._M_value,
> std::min(ranges::distance(__r), __n));
> + else
> + return views::repeat(*__r._M_value, __n);
> + }
> +
> + template<typename _Range>
> + constexpr auto
> + __drop_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n)
> + {
> + using _Tp = remove_cvref_t<_Range>;
> + static_assert(__is_repeat_view<_Tp>);
> + if constexpr (sized_range<_Tp>)
> + {
> + auto __sz = ranges::distance(__r);
> + return views::repeat(*__r._M_value, __sz - std::min(__sz,
> __n));
> + }
> + else
> + return __r;
> + }
> + }
> }
>
> template<input_range _Vp>
> diff --git a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
> b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
> index 3698ed12c14..542c8614f88 100644
> --- a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
> @@ -84,10 +84,43 @@ test03()
> return true;
> }
>
> +constexpr bool
> +test04()
> +{
> + // Verify P2472R2 changes to views::take/drop.
> + auto r = views::repeat(42);
> +
> + auto rt = r | views::take(10);
> + static_assert(views::__detail::__is_repeat_view<decltype(rt)>);
> + VERIFY( ranges::equal(rt, views::repeat(42, 10)) );
> +
> + auto rd = r | views::drop(10);
> + static_assert(std::same_as<decltype(rd), decltype(r)>);
> +
> + auto br = views::repeat(42, 37);
> +
> + auto brt = br | views::take(10);
> + static_assert(std::same_as<decltype(brt), decltype(br)>);
> + VERIFY( ranges::equal(brt, views::repeat(42, 10)) );
> +
> + auto brt100 = br | views::take(100);
> + VERIFY( ranges::equal(brt100, br) );
> +
> + auto brd = br | views::drop(10);
> + static_assert(std::same_as<decltype(brd), decltype(br)>);
> + VERIFY( ranges::equal(brd, views::repeat(42, 27)) );
> +
> + auto brd100 = br | views::drop(100);
> + VERIFY( ranges::empty(brd100) );
> +
> + return true;
> +}
> +
> int
> main()
> {
> static_assert(test01());
> static_assert(test02());
> static_assert(test03());
> + static_assert(test04());
> }
> --
> 2.38.1.119.g9c32cfb49c
>
>
@@ -2257,6 +2257,13 @@ namespace views::__adaptor
template<typename _Winc, typename _Bound>
inline constexpr bool __is_iota_view<iota_view<_Winc, _Bound>> = true;
+ template<typename _Range>
+ inline constexpr bool __is_repeat_view = false;
+
+ template<typename _Range>
+ constexpr auto
+ __take_of_repeat_view(_Range&&, range_difference_t<_Range>); // defined later
+
template<typename _Range, typename _Dp>
concept __can_take_view
= requires { take_view(std::declval<_Range>(), std::declval<_Dp>()); };
@@ -2291,6 +2298,8 @@ namespace views::__adaptor
else
return iota_view(*__begin, *__end);
}
+ else if constexpr (__detail::__is_repeat_view<_Tp>)
+ return __detail::__take_of_repeat_view(std::forward<_Range>(__r), __n);
else
return take_view(std::forward<_Range>(__r), __n);
}
@@ -2527,6 +2536,10 @@ namespace views::__adaptor
{
namespace __detail
{
+ template<typename _Range>
+ constexpr auto
+ __drop_of_repeat_view(_Range&&, range_difference_t<_Range>); // defined later
+
template<typename _Range, typename _Dp>
concept __can_drop_view
= requires { drop_view(std::declval<_Range>(), std::declval<_Dp>()); };
@@ -2568,6 +2581,8 @@ namespace views::__adaptor
else
return _Tp(__begin, __end);
}
+ else if constexpr (__detail::__is_repeat_view<_Tp>)
+ return __detail::__drop_of_repeat_view(std::forward<_Range>(__r), __n);
else
return drop_view(std::forward<_Range>(__r), __n);
}
@@ -7367,6 +7382,14 @@ namespace views::__adaptor
struct _Iterator;
+ template<typename _Range>
+ friend constexpr auto
+ views::__detail::__take_of_repeat_view(_Range&&, range_difference_t<_Range>);
+
+ template<typename _Range>
+ friend constexpr auto
+ views::__detail::__drop_of_repeat_view(_Range&&, range_difference_t<_Range>);
+
public:
repeat_view() requires default_initializable<_Tp> = default;
@@ -7540,6 +7563,9 @@ namespace views::__adaptor
{
namespace __detail
{
+ template<typename _Tp, typename _Bound>
+ inline constexpr bool __is_repeat_view<repeat_view<_Tp, _Bound>> = true;
+
template<typename _Tp>
concept __can_repeat_view
= requires { repeat_view(std::declval<_Tp>()); };
@@ -7565,6 +7591,36 @@ namespace views::__adaptor
};
inline constexpr _Repeat repeat;
+
+ namespace __detail
+ {
+ template<typename _Range>
+ constexpr auto
+ __take_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n)
+ {
+ using _Tp = remove_cvref_t<_Range>;
+ static_assert(__is_repeat_view<_Tp>);
+ if constexpr (sized_range<_Tp>)
+ return views::repeat(*__r._M_value, std::min(ranges::distance(__r), __n));
+ else
+ return views::repeat(*__r._M_value, __n);
+ }
+
+ template<typename _Range>
+ constexpr auto
+ __drop_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n)
+ {
+ using _Tp = remove_cvref_t<_Range>;
+ static_assert(__is_repeat_view<_Tp>);
+ if constexpr (sized_range<_Tp>)
+ {
+ auto __sz = ranges::distance(__r);
+ return views::repeat(*__r._M_value, __sz - std::min(__sz, __n));
+ }
+ else
+ return __r;
+ }
+ }
}
template<input_range _Vp>
@@ -84,10 +84,43 @@ test03()
return true;
}
+constexpr bool
+test04()
+{
+ // Verify P2472R2 changes to views::take/drop.
+ auto r = views::repeat(42);
+
+ auto rt = r | views::take(10);
+ static_assert(views::__detail::__is_repeat_view<decltype(rt)>);
+ VERIFY( ranges::equal(rt, views::repeat(42, 10)) );
+
+ auto rd = r | views::drop(10);
+ static_assert(std::same_as<decltype(rd), decltype(r)>);
+
+ auto br = views::repeat(42, 37);
+
+ auto brt = br | views::take(10);
+ static_assert(std::same_as<decltype(brt), decltype(br)>);
+ VERIFY( ranges::equal(brt, views::repeat(42, 10)) );
+
+ auto brt100 = br | views::take(100);
+ VERIFY( ranges::equal(brt100, br) );
+
+ auto brd = br | views::drop(10);
+ static_assert(std::same_as<decltype(brd), decltype(br)>);
+ VERIFY( ranges::equal(brd, views::repeat(42, 27)) );
+
+ auto brd100 = br | views::drop(100);
+ VERIFY( ranges::empty(brd100) );
+
+ return true;
+}
+
int
main()
{
static_assert(test01());
static_assert(test02());
static_assert(test03());
+ static_assert(test04());
}