Since the last time I was sent a reply regarding this proposal, I have written a draft paper to submit. I will send it here first in hope for mistakes I didn't catch, may they be grammatical or logical.

Thank you for the feedback I got. Here's a draft of the paper written in Google Docs, and of course, a link to the GitHub implementation.

On Sat, 14 Mar 2026 at 13:13, Emanuel Spiridon <spiridonemanuel23@gmail.com> wrote:

> C++ currently has no way to create a named and reusable set of types that can be used as a concept constraint. Every time you write a concept constraint or requires section, you must enumerate the types, which makes large constraints unreadable and unmaintainable.

> I propose a solution, a type with template arguments for any type, including user-defined types and standard library types, which you can then use when creating a concept or requires section, by stating the named type list and the type you want to check.

> Here is how my implementation works:

> template<typename T>
> 	requires std::is_same_v<T, unsigned char> || std::is_same_v<T, unsigned short> || std::is_same_v<T, unsigned int> || std::is_same_v<T, unsigned long> || std::is_same_v<T, unsigned long long>
> void natural_only(T);
> template<typename T>
> 	requires std::is_same_v<T, unsigned char> || std::is_same_v<T, unsigned short> || std::is_same_v<T, unsigned int> || std::is_same_v<T, unsigned long> || std::is_same_v<T, unsigned long long> || std::is_same_v<T, char> || std::is_same_v<T, short> || std::is_same_v<T, int> || std::is_same_v<T, long> || std::is_same_v<T, long long>
> void whole_only(T);
>
> using natural_numbers = typename tag::merge_tags_and_types<unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long>::type;
> using whole_numbers   = typename tag::merge_tags_and_types<signed char, short, int, long, long long, natural_numbers>::type;
> using real_numbers    = typename tag::merge_tags_and_types<float, double, long double>::type;
> using numbers         = typename tag::merge_tags_and_types<whole_numbers, real_numbers>::type;
>
> template<typename T>
> concept is_number = tag::contains<numbers, T>;
> 
> template<typename T>
> concept is_whole = tag::contains<whole_numbers, T>;
> 
> template<typename T>
> concept is_natural = tag::contains<natural_numbers, T>;
> 
> template<typename T>
> concept is_real = tag::contains<real_numbers, T>;
> 
> template<typename T>
> 	requires tag::contains<natural_numbers, T>
> void natural_only(T);
> 
> 
> You can read the source of the implementation at Github. A paper draft is forthcoming
> 
> I am looking for feedback before submitting a formal paper.