On Mon, 29 Mar 2021, Patrick Palka wrote:
> The <ranges> header currently copies some simple algorithms from
> <bits/ranges_algo.h>, which was originally done in order to avoid a
> circular dependency with the header. This is no longer an issue since
> the latter header now includes <bits/ranges_util.h> instead of all of
> <ranges>.
>
> This means we could now just include <bits/ranges_algo.h> and remove the
> copied algorithms, but that would double the size of <ranges>.
Whoops, more like increase the size of <ranges> by ~10% (33k SLOC -> 37k).
> And we
> can't use the corresponding STL-style algorithms here because they
> assume input iterators are copyable. So this patch instead simplifies
> these copied algorithms, removing their constraints and unused
> parameters, and keeps them around. In a subsequent patch we're going to
> copy ranges::find into <ranges> as well.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/ranges (__detail::find_if): Simplify.
> (__detail::find_if_not): Likewise.
> (__detail::min): Remove.
> (__detail::mismatch): Simplify.
> (take_view::size): Use std::min instead of __detail::min.
> ---
> libstdc++-v3/include/std/ranges | 59 ++++++++++-----------------------
> 1 file changed, 17 insertions(+), 42 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index cfcbcaba065..9077271e4e6 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -978,65 +978,40 @@ namespace views::__adaptor
> using all_t = decltype(all(std::declval<_Range>()));
> } // namespace views
>
> - // XXX: the following algos are copied from ranges_algo.h to avoid a
> circular
> - // dependency with that header.
> + // The following simple algos are transcribed from ranges_algo.h to avoid
> + // having to include that entire header.
> namespace __detail
> {
> - template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
> - typename _Proj = identity,
> - indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
> + template<typename _Iter, typename _Sent, typename _Pred>
> constexpr _Iter
> - find_if(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {})
> + find_if(_Iter __first, _Sent __last, _Pred __pred)
> {
> while (__first != __last
> - && !(bool)std::__invoke(__pred, std::__invoke(__proj, *__first)))
> + && !(bool)std::__invoke(__pred, *__first))
> ++__first;
> return __first;
> }
>
> - template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
> - typename _Proj = identity,
> - indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
> + template<typename _Iter, typename _Sent, typename _Pred>
> constexpr _Iter
> - find_if_not(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj =
> {})
> + find_if_not(_Iter __first, _Sent __last, _Pred __pred)
> {
> while (__first != __last
> - && (bool)std::__invoke(__pred, std::__invoke(__proj, *__first)))
> + && (bool)std::__invoke(__pred, *__first))
> ++__first;
> return __first;
> }
>
> - template<typename _Tp, typename _Proj = identity,
> - indirect_strict_weak_order<projected<const _Tp*, _Proj>>
> - _Comp = ranges::less>
> - constexpr const _Tp&
> - min(const _Tp& __a, const _Tp& __b, _Comp __comp = {}, _Proj __proj =
> {})
> - {
> - if (std::__invoke(std::move(__comp),
> - std::__invoke(__proj, __b),
> - std::__invoke(__proj, __a)))
> - return __b;
> - else
> - return __a;
> - }
> -
> - template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
> - input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
> - typename _Pred = ranges::equal_to,
> - typename _Proj1 = identity, typename _Proj2 = identity>
> - requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
> + template<typename _Iter1, typename _Sent1, typename _Iter2, typename
> _Sent2>
> constexpr pair<_Iter1, _Iter2>
> - mismatch(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2
> __last2,
> - _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {})
> + mismatch(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2
> __last2)
> {
> while (__first1 != __last1 && __first2 != __last2
> - && (bool)std::__invoke(__pred,
> - std::__invoke(__proj1, *__first1),
> - std::__invoke(__proj2, *__first2)))
> - {
> - ++__first1;
> - ++__first2;
> - }
> + && (bool)ranges::equal_to{}(*__first1, *__first2))
> + {
> + ++__first1;
> + ++__first2;
> + }
> return { std::move(__first1), std::move(__first2) };
> }
> } // namespace __detail
> @@ -1847,14 +1822,14 @@ namespace views::__adaptor
> size() requires sized_range<_Vp>
> {
> auto __n = ranges::size(_M_base);
> - return __detail::min(__n, static_cast<decltype(__n)>(_M_count));
> + return std::min(__n, static_cast<decltype(__n)>(_M_count));
> }
>
> constexpr auto
> size() const requires sized_range<const _Vp>
> {
> auto __n = ranges::size(_M_base);
> - return __detail::min(__n, static_cast<decltype(__n)>(_M_count));
> + return std::min(__n, static_cast<decltype(__n)>(_M_count));
> }
> };
>
> --
> 2.31.1.133.g84d06cdc06
>
>
