Is it possible to force CTFE?

[bearophile]

Jacob Carlborg:

>> I am interested in this since some years. I think it's useful, 
>> but I don't know if it can be implemented. I don't remember
>> people discussing about this much.
>
> There's the if (__ctfe) hack. Also using only template 
> parameters will force the function to be CTFE.

This is quite far from what I was discussing about here...

Bye,
bearophile