Why isn't opMul allowed in a const expression

[Steven Schveighoffer]

"torhu" wrote
> Steven Schveighoffer wrote:
>> I added:
>>
>>   static X tmpOpMul(X x, int y)
>>   {
>>     return X(x.value * y);
>>   }
>>
>> To X, and I can do:
>>
>> static myX4 = X.tmpOpMul(myX, 4);
>>
>> without error.  I don't see how this is any different than calling opMul. 
>> It should be evaluatable at compile time, no?
>>
>
> For initializing a constant you need a compile-time value.
>
> From the docs about compile-time functions:
> "4. the function may not be a non-static member, i.e. it may not have a 
> this pointer"

Yep, you are right.

There needs to be a change here.  Either:
1. I need to be able to specify opX as a static function, where opX is a 
binary math operator.
2. I need to be able to use struct member functions as long as they adhere 
to the other rules of CTFE.

I don't think this request is unreasonable.  Structs are different from 
classes in that all member functions are final.  So there is no question as 
to calling a virtual method, or how to construct a struct object to call the 
method with.

Without something of this nature, I can't create a true value type.

Walter, is something like this being planned?

-Steve