Inherit from class based on bool value

[bauss]

On Thursday, 15 November 2018 at 08:46:36 UTC, Bienlein wrote:
> On Tuesday, 13 November 2018 at 07:10:26 UTC, Jamie wrote:
>> I would like my class to inherit from one of two classes based 
>> on a boolean value known at compile time. Something like this:
>>
>> void main()
>> {
>>     Top!(OPTION.FALSE) top = new Top!(OPTION.FALSE);
>> }
>>
>> enum OPTION
>> {
>>     FALSE = 0.,
>>     TRUE = 1.
>> }
>>
>> class One
>> {}
>>
>> class Two
>> {}
>>
>> class Top(OPTION option) : option ? One : Two
>> {}
>>
>> Is this possible? I can't get it to work in the way I'm 
>> showing above.
>> Cheers
>
> My piece of advice would be not to do this but to model all 
> data explicitly. And I had some exposure to OOP with over 10 
> years developing in Smalltalk, which is a pure OO language. 
> Actually, I don't know whether it is good that this can be done 
> in D ...

It's really no different than doing it manually and it's prettier 
than if it was done using a mixin, in which you'd not be able to 
limit it at all.

D is not an OOP language and it doesn't even conform to standard 
OOP practices so really it doesn't matter.

What doesn't make sense in one language, might make sense in 
another language.

I feel like restrictions often limit the full potential of a 
language, more often than it damages it.

Depending on the use-case this might make sense. It would 
actually be very useful for exceptions/errors in D.

Something like:

template ExceptionParent(Parent = Exception)
{
    static if (flagsThatDeterminesItsDebugMode)
    {
        alias ExceptionParent = Error;
    }
    else
    {
        alias ExceptionParent = Parent;
    }
}

class MyException : ExceptionParent!()
{
     ...
}

Now when debugging all exceptions will be error and when it's not 
debugging it'll be an exception.