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libstdc++: P1970R2 Consistency for size() functions: Add ranges::ssize

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This defines ranges::ssize as approved in Prague. It's unclear what is
supposed to happen for types for which range_difference_t is not a valid
type. I've assumed they are not meant to be usable with ranges::ssize,
despite being usable with ranges::size.

	* include/bits/range_access.h (_SSize, ssize): Define for C++20.
	* testsuite/std/ranges/access/ssize.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-02-17 17:58:09 +00:00
parent 9866abe31e
commit 7ab36231a1
3 changed files with 130 additions and 0 deletions
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4
libstdc++-v3/ChangeLog
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@ -1,5 +1,9 @@
2020-02-17 Jonathan Wakely <jwakely@redhat.com>
P1970R2 Consistency for size() functions: Add ranges::ssize
* include/bits/range_access.h (_SSize, ssize): Define for C++20.
* testsuite/std/ranges/access/ssize.cc: New test.
P1956R1 On the names of low-level bit manipulation functions
* include/bits/hashtable_policy.h: Update comment.
* include/std/bit (__ispow2, __ceil2, __floor2, __log2p1): Rename.

28
libstdc++-v3/include/bits/range_access.h
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@ -35,6 +35,7 @@
#if __cplusplus >= 201103L
#include <initializer_list>
#include <bits/iterator_concepts.h>
#include <bits/int_limits.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
@ -723,6 +724,32 @@ namespace ranges
}
};
struct _SSize
{
template<typename _Tp>
requires requires (_Tp&& __e)
{
_Begin{}(std::forward<_Tp>(__e));
_Size{}(std::forward<_Tp>(__e));
}
constexpr auto
operator()(_Tp&& __e) const
noexcept(noexcept(_Size{}(std::forward<_Tp>(__e))))
{
using __iter_type = decltype(_Begin{}(std::forward<_Tp>(__e)));
using __diff_type = iter_difference_t<__iter_type>;
using std::__detail::__int_limits;
auto __size = _Size{}(std::forward<_Tp>(__e));
if constexpr (integral<__diff_type>)
{
if constexpr (__int_limits<__diff_type>::digits
< __int_limits<ptrdiff_t>::digits)
return static_cast<ptrdiff_t>(__size);
}
return static_cast<__diff_type>(__size);
}
};
template<typename _Tp>
concept __member_empty = requires(_Tp&& __t)
{ bool(std::forward<_Tp>(__t).empty()); };
@ -834,6 +861,7 @@ namespace ranges
inline constexpr __cust_access::_CRBegin crbegin{};
inline constexpr __cust_access::_CREnd crend{};
inline constexpr __cust_access::_Size size{};
inline constexpr __cust_access::_SSize ssize{};
inline constexpr __cust_access::_Empty empty{};
inline constexpr __cust_access::_Data data{};
inline constexpr __cust_access::_CData cdata{};

98
libstdc++-v3/testsuite/std/ranges/access/ssize.cc Normal file
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@ -0,0 +1,98 @@
// Copyright (C) 2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do run { target c++2a } }
#include <ranges>
#include <testsuite_hooks.h>
#include <testsuite_iterators.h>
using std::ptrdiff_t;
void
test01()
{
constexpr int a[10] = { };
static_assert( std::same_as<decltype(std::ranges::ssize(a)), ptrdiff_t> );
static_assert( std::ranges::ssize(a) == 10 );
static_assert( noexcept(std::ranges::ssize(a)) );
int a2[2];
static_assert( std::same_as<decltype(std::ranges::ssize(a2)), ptrdiff_t> );
VERIFY( std::ranges::ssize(a2) == 2);
static_assert( noexcept(std::ranges::ssize(a2)) );
struct Incomplete;
using A = Incomplete[2]; // bounded array of incomplete type
extern A& f();
static_assert( std::same_as<decltype(std::ranges::ssize(f())), ptrdiff_t> );
}
void
test02()
{
int a[3] = { };
__gnu_test::test_sized_range<int, __gnu_test::input_iterator_wrapper> ri(a);
VERIFY( std::ranges::ssize(ri) == 3 );
static_assert( noexcept(std::ranges::ssize(ri)) );
}
void
test04()
{
int a[] = { 0, 1 };
__gnu_test::test_range<int, __gnu_test::random_access_iterator_wrapper> r(a);
VERIFY( std::ranges::ssize(r) == std::ranges::end(r) - std::ranges::begin(r) );
}
struct R5
{
int size() const noexcept { return 0; }
R5* begin() { return this; }
R5* end() { return this + 1; }
};
template<>
constexpr bool std::ranges::disable_sized_range<R5> = true;
void
test05()
{
R5 r;
VERIFY( std::ranges::ssize(r) == 1 );
}
void
test06()
{
auto i = std::views::iota(1ull, 5);
auto s = std::ranges::ssize(i);
using R = std::ranges::range_difference_t<decltype(i)>;
static_assert( std::same_as<decltype(s), R> );
VERIFY( s == 4 );
}
int
main()
{
test01();
test02();
test04();
test05();
test06();
}