śr., 12 mar 2025 o 23:46 Dmitrii Shabalin via Std-Proposals
<std-proposals_at_[hidden]> napisał(a):
>
> 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.
>

There is a simple solution: `;`
List of values in enums end with `;` and this part start of member
functions and similar things.
```
enum class E {
   A = 1, B = getSometing(), C = 3
   , // last comma to still allow standard formatting of `,` after each value
   ; // <- here! end of values

   //now parsing is similar to `class`, you can't declare new values of enum.
   bool foo();
   E getSometing();
};
```

> 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);
>>>>> --
>>>>> Std-Proposals mailing list
>>>>> Std-Proposals_at_[hidden]
>>>>> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>>>>
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