Re: [boost] Visitation using RTTI

From: Stefan Seefeld (seefeld_at_[hidden])
Date: 2008-03-28 18:21:30

Mathias Gaunard wrote:
> Stefan Seefeld wrote:
> 
>> I agree. And, some simpler templating techniques may be used to map the 
>> current helt type discriminator to the (C++) type, thus dispatching 
>> calls by other means than what is typically referred to as 'visitation'.
> 
> What techniques?

As I understand your request, you want to roll your own switch 
statement, but with more expressive values than simple numbers. In other 
words, you want a mapping from types to variant type discriminators:

variant<A, B, C> v = ....;
switch (v.which())
{
   case v::type_id<A>::value: break;
   case v::type_id<B>::value: break;
}

(there are certainly many ways to spell that 'type_id' map above, I just 
made this up to illustrate my point.)

>> (I still fail to appreciate the usefulness of those compile-time static 
>> strings. I find them rather ugly...)
> 
> If you want to compute something on a string at compile-time, you need a 
> compile-time string.

Certainly. But I haven't seen any good example on *what* I may want to 
compute on a string at compile-time. To me...

struct my_compile_time_string;

...makes 'my_compile_time_string' a very lean and easy-to-read 
compile-time string. And as far as I know it's in use in boost in a lot 
of places already (not the least to generate intelligible compiler error 
messages, triggered during template instantiations).

Regards,
                Stefan

-- 
       ...ich hab' noch einen Koffer in Berlin...