I am sorry if I am disturbing, but I just wanted to show that my main code
is done (only a little is left to be completed for the basic use to be
compiled). I will do the rest tomorrow but yeah, the pattern is
beautiful but a little costly though (the complexity in practice shortens
as the data grows). I am sending this email because I enjoyed making this
and I think that you guys will as well, and that you guys will see the
beauty of this pattern:
https://github.com/HjaldrKhilji/C-and-C-plus-plus-notes/blob/main/extended%20enum%20example
https://onlinegdb.com/8tt9dxa6c

On Tue, Apr 28, 2026 at 9:37 AM Muneem <itfllow123_at_[hidden]> wrote:

> I was just trying to make some conversation, like the scope of these kind
> of tricks is a lot. We can literally change metaprogramming if we can allow
> inheritance like behaviour that is not only lightweight but in practice
> feels like a built in type. Showing the process was to like show that while
> it is hard and you will hit wall, it is not impossible, even for me. I do
> get that I should've made it short and way fewer emails, but yeah, I will
> do that from now on.
>
> On Mon, 27 Apr 2026, 10:57 pm Sebastian Wittmeier via Std-Proposals, <
> std-proposals_at_[hidden]> wrote:
>
>> I think this list is not good for giving frequent updates on
>> implementations of features, especially not central for understanding or
>> especially if the implementation is not finished.
>>
>>
>>
>> If Andrey Fokin directly wants to work on an implementation, you can
>> coordinate.
>>
>> But frequent implementations updates is (IMHO) a bit too noisy here. Some
>> other posters have done the same and got respective feedback.
>>
>>
>>
>> Not to curb your enthusiasm, just to focus your emails better. And all is
>> in MHO.
>>
>>
>>
>> Sebastian
>>
>>
>>
>>
>> -----Ursprüngliche Nachricht-----
>> *Von:* Muneem via Std-Proposals <std-proposals_at_[hidden]>
>> *Gesendet:* Mo 27.04.2026 18:59
>> *Betreff:* Re: [std-proposals] Add inheritance for Enum Class
>> enumerations
>> *An:* std-proposals_at_[hidden];
>> *CC:* Muneem <itfllow123_at_[hidden]>;
>> Sorry for obsessing too much over the implementation and sending too many
>> emails. I am obsessed with this enum inheritance support because any
>> technique of allowing stateful metaprogramming should be treasured, as long
>> as it's not one of those wierd freind injecting techniques. In my case, I
>> am checking is a specialization exists, to find a unique number which I use
>> to stack static constexpr enums. Each class specializations has its own
>> stack of these enums. If I manage to make this enum inheritance work then
>> maybe we will have a time where you can feed "nueral network"/prediction
>> paremeter data through compiler paremeters, and use the values and types of
>> say these enums with hirearchies, to make decisions on what the type and
>> data of later enums objects that are in a Hirearchy should be. Basically,
>> it could allow for lightweight compile time polymorphism. The technique
>> looks like this to get a number:
>> template<template<std::uintmax_t N_> class C, std::uintmax_t N>
>> struct exist {
>> template<typename exist_if_exist= decltype(std::declval<C<N>>().~C<N>())>
>> bool static does() {
>> return true;
>> }
>> bool static does() {
>> exist<sequential_count, N+1> dummy{};
>>
>> return false;
>> }
>> };
>>
>> namespace {
>> template<std::uintmax_t N=0>
>> struct sequential_count {
>>
>> consteval static std::uintmax_t get_num() {
>>
>> if(exist<sequential_count, N+1>::does()) {
>> return sequential_count<N+2>::get_num()
>>
>> }
>> else {
>> return N+1;
>> }
>> }
>>
>> };
>>
>> }
>> Once you have a number, you could use that to get a new type for that
>> specific class Hirearchy object. Each object has its own hirarchy cuz each
>> object has a default argument that gets a unique number this way. You could
>> add a wrapper that basically does the same as get_num but instead it checks
>> if N*b exists and if it does then: return N*b if N*b minus 1 does not exist,
>> Else if N*b-b does not exist then call a linear search that returns
>> N+linear_search,
>> else return N+the_whole_process_from_n_being_1.
>> The goal is to expand metaprogramming into something with state.
>>
>>
>> On Mon, 27 Apr 2026, 4:08 pm Muneem, <itfllow123_at_[hidden]> wrote:
>>
>> I did finished till here for today ( a lot still left ):
>> https://onlinegdb.com/AUyKksvtW
>>
>> https://github.com/HjaldrKhilji/C-and-C-plus-plus-notes/blob/main/extended%20enum%20example
>> Credits to:
>> https://www.lukas-barth.net/blog/checking-if-specialized/
>> For helping me find a technique to see if a type has been instantiated or
>> not, which really helped me to like do the stateful metaprogramming thing.
>> Unlike the unfortunate "get obj" technique, this one will hopefully work!
>>
>> On Mon, 27 Apr 2026, 1:53 pm Muneem, <itfllow123_at_[hidden]> wrote:
>>
>> Looks like my consteval workaround to get a static class data member to
>> be constant dosent work. It's a shame but I will find a technique, it's
>> just this one thing. Sorry for the delay, like I get this should've been
>> trivial but sometimes you gotta hack into the language, which isn't as
>> straightforward as I thought it would be.
>>
>> On Sun, 26 Apr 2026, 6:32 pm Muneem, <itfllow123_at_[hidden]> wrote:
>>
>> In case anyone is confused by my ad hoc pattern: it's basically stateful
>> metaprogramming such that each enum object has a new type. This stateful
>> metaprogramming technique is (for the lack of a better word) "Appending
>> pattern":
>> //it looks something like this:
>> //This pattern wont cause issues in multiple translation units because
>> you are basically appending and the part where you create the "red
>> apple"(the part where the data exist) is when you append. Since the
>> appending(not overwriting) part is literally spending hence there should be
>> no issues.
>> template<typename T, T* obj>
>> consteval T get_obj() {
>> return *obj;
>> }
>>
>> template<typename T, std::uintmax_t N>
>> struct The_red_apple{
>> inline static bool v = false;
>>
>> inline static T data;//get_obj can also be used to pass this as a
>> template argument
>> };
>> template<typename T, std::uintmax_t N=0, bool v=get_obj<bool,&
>> type_exists<T, N>::v>()>
>> struct get_the_type{
>> using type_found=
>> std::conditional_t<
>> v,
>> typename get_the_type <T, N+1>::internal_t,
>> The_red_apple <T, N>
>> >;
>> type_found ::v= true;// the type was already appended hence no
>> issues (like no issues of overwriting an existing type's static data)
>> static const constexpr std::uintmax_t N_val= N; //could be used further
>> down the tree just line in my original (but incomplete code).
>> //sorry if my original code (since it was incomplete) made this simple
>> pattern look ad hoc and bad
>> }
>>
>> On Sun, Apr 26, 2026 at 4:07 PM Muneem <itfllow123_at_[hidden]> wrote:
>>
>> My "extended enums" when complete could be equavilent to constexpr normal
>> enums, like normally the input to enum is constexpr anyway so this should
>> be okay. One could further provide more functions that if the enum is
>> runtime initliazed or Assigned at runtime then the return value is a simple
>> uintmax_t or another variant. Once the code is finished, I would try to do
>> that and also show an example of how to implement multiple inheritance on
>> it.
>>
>> On Sun, 26 Apr 2026, 3:41 pm Muneem, <itfllow123_at_[hidden]> wrote:
>>
>> I will finish the rest of the code tomorrow but please please criticize
>> it. There is a saying in pashto that goes something like "success is
>> sweating and hardwork". In my case the sweat and hardwork is contributing,
>> and being criticized for my mistakes so I can change my way of thinking
>> regarding the particular concept in whose application I did a mistake in.
>> Like again, there are a billion ways to implement extended enums, but the
>> ones used are the ones that are made so let's make one.
>>
>> On Sun, 26 Apr 2026, 3:26 pm Muneem, <itfllow123_at_[hidden]> wrote:
>>
>> Let's please talk about implementation:
>>
>> https://github.com/HjaldrKhilji/C-and-C-plus-plus-notes/blob/main/extended%20enum%20example
>> https://onlinegdb.com/5raHnqV7e
>> Like my code is not complete but please criticize it. My previous code
>> had an issue with non constant expression being used but then I tried some
>> fixes, so please tell me what you think. Like ideas are all good but I am
>> really excited to see this idea work first. I know like I am new to all
>> this so really haven't earned my seat at the table, but in my humble
>> opinion, the design only makes sense when it's in the code.
>>
>> On Sun, 26 Apr 2026, 11:19 am Simon Schröder via Std-Proposals, <
>> std-proposals_at_[hidden]> wrote:
>>
>>
>>
>> > On Apr 25, 2026, at 7:38 PM, Marcin Jaczewski via Std-Proposals <
>> std-proposals_at_[hidden]> wrote:
>> >
>> > sob., 25 kwi 2026 o 10:03 Jens Maurer via Std-Proposals
>> > <std-proposals_at_[hidden]> napisał(a):
>> >>
>> >>
>> >>
>> >>> On 4/25/26 01:11, Sebastian Wittmeier via Std-Proposals wrote:
>> >>> They could have different underlying representations:
>> >>
>> >> Yes.
>> >>
>> >>> With strong typing the compiler could add an offset for one of the
>> ancestor enum classes.
>> >>
>> >> No, that won't work.
>> >>
>> >>
>> >> If this hypothetical feature is just for re-using enum values
>> >> and allowing conversion from a "base" value to a "derived" enum type,
>> >> then maybe there's some merit hidden here. However, I can't see how
>> >> to make a "Derived*" convert to a "Base*", similar to class derivation.
>> >>
>> >>
>> >> Alternative syntax suggestion:
>> >>
>> >> enum class Derived {
>> >> using enum Base; // import the enumerators here; ugh, semicolon
>> >> NEXT_ENUM = whatever,
>> >> };
>> >
>> > or maybe better would simply allow user-defined conversion functions
>> for enums.
>> > Then we could allow conversion from `Base` to `Derived`.
>>
>> Even if we can define conversion functions this would still leave the
>> problem that we would have to retype all enumerations of Base inside
>> Derived (and not forget that when we add one in Base later). As far as I
>> understand the main goal is to subsume all enumerations from Base in
>> Derived. Having *all* the enumerations is especially important when
>> switching over them (compilers give warnings when leave one out when using
>> enum classes).
>> >
>> >
>> >>
>> >> Jens
>> >>
>> >>
>> >>>
>> >>> -----Ursprüngliche Nachricht-----
>> >>> *Von:* Arthur O‘Dwyer via Std-Proposals <
>> std-proposals_at_[hidden]>
>> >>> *Gesendet:* Fr 24.04.2026 23:10
>> >>> *Betreff:* Re: [std-proposals] Add inheritance for Enum
>> Class enumerations
>> >>> *An:* std-proposals_at_[hidden];
>> >>> *CC:* Arthur O‘Dwyer <arthur.j.odwyer_at_[hidden]>;
>> >>>> On Fri, Apr 24, 2026 at 4:00 PM Gašper Ažman via Std-Proposals <
>> std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>>
>> wrote:
>> >>>
>> >>> Note that `using enum` exists and probably does what you need.
>> >>>
>> >>>
>> >>> I don't think "using enum" does what Andrey wants — because I
>> think Andrey is trying to describe this other common problem instead. This
>> /r/ProgrammingLanguages thread <
>> https://www.reddit.com/r/ProgrammingLanguages/comments/rk1y4u/extending_enums/>
>> calls it "extending enums."
>> >>> Here's some lightly-anonymized code from a real (DNS-related)
>> codebase:
>> >>>
>> >>> enum HttpServerStat {
>> >>> TLS_HANDSHAKES,
>> >>> TLS_HANDSHAKE_ERRORS,
>> >>> TLS_HANDSHAKE_TIMEOUTS,
>> >>> [...]
>> >>> RESPONSE_DROPS,
>> >>> MAX_HTTP_SERVER_STAT_ID
>> >>> };
>> >>>
>> >>> enum HttpStat {
>> >>> // Extends HttpServerStat
>> >>> QUERY_COUNT_HTTP = MAX_HTTP_SERVER_STAT_ID,
>> >>> QUERY_BYTES_HTTP,
>> >>> RESPONSE_COUNT_HTTP,
>> >>> RESPONSE_BYTES_HTTP,
>> >>> [...]
>> >>> MAX_HTTP_STAT_ID
>> >>> };
>> >>>
>> >>> enum ODoHStat {
>> >>> // Extends HttpStat
>> >>> ODOH_QUERY_COUNT = MAX_HTTP_STAT_ID,
>> >>> ODOH_QUERY_BYTES,
>> >>> [...]
>> >>> ODOH_4XX_RESPONSE,
>> >>> MAX_ODOH_STAT_ID
>> >>> };
>> >>>
>> >>> (Sidebar: We had to make some very minor changes to the users of
>> this code for C++20, which tightened restrictions on cross-enum arithmetic
>> and comparison.)
>> >>> The idea is that ODoHStat "extends" HttpStat in the same way that
>> std::partial_ordering "extends" std::strong_ordering. Every value in the
>> domain of HttpStat is also in the domain of ODoHStat (although the reverse
>> is not true).
>> >>> Notice that this is the opposite of what class inheritance means!
>> When a /class/ ODoHStat /derives/ from HttpStat then we say that every
>> object of type ODoHStat is an object of type HttpStat (not the reverse).
>> >>>
>> >>> What we really want to be able to say here is something like
>> >>> enum class ODoHStat : using HttpStat {
>> >>> ODOH_QUERY_COUNT = MAX_HTTP_STAT_ID,
>> >>> ODOH_QUERY_BYTES,
>> >>> [...]
>> >>> ODOH_4XX_RESPONSE,
>> >>> MAX_ODOH_STAT_ID
>> >>> };
>> >>> Again, notice the inappropriateness of "inheritance" syntax here.
>> >>> enum ODoHStat : HttpStat { // NO!
>> >>> Because that syntax already has a meaning for enum declarations:
>> it's "HttpStat is the underlying type of ODoHStat; we guarantee that all
>> values of type ODoHStat will fit into an HttpStat." Which is /*not at all*/
>> what we mean here; in fact we mean the opposite: here we guarantee that all
>> values of type /HttpStat/ will fit into an /ODoHStat/.
>> >>>
>> >>> This fantasy feature would permit us to use `enum class`, and
>> expose all the enumerators of the "parent" enum as members of the "child",
>> thus:
>> >>> ODoHStat e = ODoHStat::QUERY_COUNT_HTTP;
>> >>> Today, we can't do that. We can either avoid scoped enums
>> altogether, or else we have to write
>> >>> ODoHStat e = static_cast<ODoHStat>(HttpStat::QUERY_COUNT_HTTP);
>> >>>
>> >>> If we got such a facility:
>> >>>
>> >>> (1) We would not want to permit the "child" enum to just start
>> listing new enumerators without an initializer for the first one:
>> >>> enum class ODoHStat : using HttpStat { ODOH_QUERY_COUNT,
>> ODOH_QUERY_BYTES, [...] // NO!
>> >>> because what would they start numbering at — zero?
>> one-more-than-the-parent-enum's-highest-enumerator?
>> std::bit_ceil-of-one-more-than-the-parent-enum's-highest-enumerator? None
>> of these are safe answers. The only safe pattern is as we do in the code
>> above: start where the parent enum tells you to start. Even then, this is
>> super fragile: if we add a new enumerator to HttpStat, that will increment
>> the values of ODoHStat's enumerators too. Arguably the author of ODoHStat
>> knew what they were signing up for when they used this facility?
>> >>>
>> >>> (2) The facility does not seem to permit "multiple inheritance,"
>> or if it does, the semantics might be surprising.
>> >>> enum class Fruit { Apple, Grape, Orange };
>> >>> enum class Color { Red, Orange, Yellow };
>> >>> enum class Thing : using Fruit, Color {};
>> >>> // both Thing::Apple and Thing::Red have value zero, right?
>> >>> // does Thing::Orange exist? what is its value?
>> >>>
>> >>> Anyway, I'm sure "extending enums" has been proposed before, but I
>> haven't yet found where. N1513 Improving Enumeration Types <
>> http://www2.open-std.org/JTC1/SC22/WG21/docs/papers/2003/n1513.pdf>
>> (2003) sketches several ideas re enums, but not this one.
>> >>>
>> >>> my $.02,
>> >>> –Arthur
>> >>>
>> >>> --
>> >>> Std-Proposals mailing list
>> >>> Std-Proposals_at_[hidden]
>> >>> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>> >>>
>> >>>
>> >>>
>> >>
>> >> --
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>> >> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>> > --
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>