On Wed, 12 Mar 2025 at 02:23, Jeremy Rifkin 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.
>
> 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) { … }
>

It might simplify things to only allow functions declared with trailing
return type or a placeholder type, so that it starts with a keyword:

auto to_string(E value) -> std::string_view { ... }

That way the parser would know right away that it's not seeing an
enumerator declaration.



> }
>
> E e = E::A;
> e.to_string();
>
>
> 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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