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From: "m.cencora at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/100157] Support `__type_pack_element` like Clang
Date: Thu, 30 Jun 2022 11:44:01 +0000	[thread overview]
Message-ID: <bug-100157-4-R9DCvZtk5h@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100157-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100157

--- Comment #5 from m.cencora at gmail dot com ---
Yeah, __is_same builtin beats custom unique-id comparisons, but it is available
only since gcc-10 so unavailable for me.

Recently I discovered this one (only works for unique types), and it is twice
as fast as __is_same in my scenarios (I guess mainly due to memoization):

template <typename T>
struct indexed_type
{
   unsigned idx;
};

template <typename ...Ts>
struct indexed_type_list : indexed_type<Ts>...
{
   constexpr indexed_type_list(unsigned i = 0)
     : indexed_type<Ts>{i++}...
   {}
};

template <typename ...Ts>
constexpr indexed_type_list<Ts...> indexed_type_list_instance;


template <typename T, typename ...Ts>
constexpr auto index_of =
static_cast<indexed_type<T>>(indexed_type_list_instance<Ts...>).idx;

Anyway, thanks for working on this topic!

  parent reply	other threads:[~2022-06-30 11:44 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20 17:44 [Bug c++/100157] New: " vittorio.romeo at outlook dot com
2021-04-21  6:21 ` [Bug c++/100157] " rguenth at gcc dot gnu.org
2022-06-29 23:27 ` redi at gcc dot gnu.org
2022-06-29 23:33 ` redi at gcc dot gnu.org
2022-06-29 23:38 ` redi at gcc dot gnu.org
2022-06-30 10:39 ` m.cencora at gmail dot com
2022-06-30 11:11 ` redi at gcc dot gnu.org
2022-06-30 11:19 ` redi at gcc dot gnu.org
2022-06-30 11:44 ` m.cencora at gmail dot com [this message]
2022-06-30 12:46 ` vittorio.romeo at outlook dot com
2022-06-30 13:05 ` redi at gcc dot gnu.org
2022-06-30 13:08 ` redi at gcc dot gnu.org
2022-06-30 13:09 ` vittorio.romeo at outlook dot com
2022-06-30 13:14 ` redi at gcc dot gnu.org
2022-11-29 15:28 ` pdimov at gmail dot com
2023-04-19 19:37 ` cvs-commit at gcc dot gnu.org
2023-04-26  6:55 ` rguenth at gcc dot gnu.org
2023-04-26  8:08 ` redi at gcc dot gnu.org

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