From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 4C3B0386EC02; Thu, 30 Jun 2022 10:39:06 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4C3B0386EC02
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 10:39:05 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: m.cencora at gmail dot com
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: redi at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 13.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: cc
Message-ID: <bug-100157-4-ZE2IYuT86J@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-100157-4@http.gcc.gnu.org/bugzilla/>
References: <bug-100157-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 30 Jun 2022 10:39:06 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100157

m.cencora at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |m.cencora at gmail dot com

--- Comment #2 from m.cencora at gmail dot com ---
Please consider also adding a builtin for fetching index of type in type li=
st.
While there are some easy implementations (like following), they are still =
not
very performant.

template <typename T>
constexpr auto uniqId()
{
    return __PRETTY_FUNCTION__;
}

template <typename U, unsigned N>
constexpr unsigned index_of_impl(U needle, const U (&haystack)[N])
{
    for (unsigned i =3D 0u; i !=3D N; ++i)
    {
        if (haystack[i] =3D=3D needle)
        {
            return i;
        }
    }
    return -1;
}

template <typename T, typename ...Ts>
constexpr auto index_of_v =3D index_of_impl(uniqId<T>, { uniqId<Ts>...});

using T1 =3D float;
using T2 =3D int;
struct A;
struct B;

auto c =3D index_of_v<A, T2, B, A, T1>;=