Hi Tom.

enum class E {
  A, B, C
  std::string_view to_string(E value) { … }
}

It would looks like a mess:

enum class E {
  A = 1, B, C = 3
  std::string_view to_string(E value) { … }
  D = A, E = calcE("E"), F
  E from_string(std::string value) { … }
 G, H, max = H
 bool IsValueExists(E Value)
}

So, you need a clear keyword to separate enumeration from functions. Or
just allow to assign a function to a value.
Second solution for me looks better.

Kind regards,
Dmitrii shabalin



чт, 13 мар. 2025 г. в 06:04, Tom Honermann via Std-Proposals <
std-proposals_at_[hidden]>:

> On 3/11/25 10:23 PM, Jeremy Rifkin via Std-Proposals wrote:
>
> Hi,
>
> > Sorry, Jeremy, but there is no straight way to add a normal function
> into enum.
> The problem is: enum is enumeration. If you stop enumeration for a
> function, it would break the logic of the enum.
>
> An implementation developer can weight in about challenge with adding this
> to existing implementations but there is no reason C++ cannot support this.
> To elaborate on what I mean, imagine syntax along the following lines:
>
> enum class E {
> A, B, C
> std::string_view to_string(E value) { … }
> }
>
> E e = E::A;
> e.to_string();
>
> I would use deducing this to support member function call syntax.
>
> enum class E {
> A, B, C;
> std::string_view to_string(this E value) { … }
> };
> E e = E::A;
> auto name = e.to_string();
>
> Tom.
>
>
>
> Cheers,
> Jeremy
>
>
> On Tue, Mar 11, 2025 at 20:23 Dmitrii Shabalin via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> Hi.
>> Sorry, Jeremy, but there is no straight way to add a normal function into
>> enum.
>> The problem is: enum is enumeration. If you stop enumeration for a
>> function, it would break the logic of the enum.
>>
>> For me, the only way is accepting a value as a function.
>>
>> Actually, it might work too:
>>
>> std::string ToString( Test test) { if (value == testValue) return
>> "testValue"; else return ""; }
>>
>> enum Test{
>> testValue = 0,
>> toString = ToString,
>> max = testValue
>> }
>>
>> std::cout << "Test value" << Test::toString(Test::testValue);
>>
>> but as you can see, it causes having a function in the different
>> namespace.
>>
>> If you have any idea how to have a function inside in the enum, please,
>> share your idea with an example.
>>
>> Kind regards,
>> Dmitrii shabalin
>>
>>
>> ср, 12 мар. 2025 г. в 12:32, Jeremy Rifkin via Std-Proposals <
>> std-proposals_at_[hidden]>:
>>
>>> Hi,
>>>
>>> It seems weird to add a special-case to just allow lambdas in enums like
>>> this. The syntax is confusing too, it resembles enum constant syntax and
>>> this isn't syntax that exists for other similar language constructs.
>>>
>>> I would much rather see enums get normal member functions like most
>>> other languages have.
>>>
>>> Cheers,
>>> Jeremy
>>>
>>>
>>> On Tue, Mar 11, 2025 at 6:20 PM Dmitrii Shabalin via Std-Proposals <
>>> std-proposals_at_[hidden]> wrote:
>>>
>>>> Hi.
>>>> Since C++11 we have lambdas.
>>>> I believe, everyone, who works with enums, write some functions for
>>>> this particular enum only.
>>>> However, there is no way to associate this function with the enum's
>>>> namespace.
>>>> My idea: we can set a value for any of enum fields. It should be const
>>>> and could be constexpr.
>>>> May be, we can set a lambda for a field too?
>>>> something like:
>>>> enum Test{
>>>> testValue = 0,
>>>> toString =[](Test value) -> std::string { if (value == testValue)
>>>> return "testValue"; else return ""; },
>>>> max = testValue
>>>> }
>>>>
>>>> And usage will be something like:
>>>> std::cout << "Test value" << Test::toString(Test::testValue);
>>>> --
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>>>>
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