Re: [boost] Re: typeof

From: Peder Holt (peder.holt_at_[hidden])
Date: 2004-09-13 15:00:58

Hi, again. 
I have done some more tinkering with the compile time constant typeof emulation.
It now compiles for VC 6.5,VC 7.0 and GCC 3.4
I have split the one argument constant into two. One per typeof
instance, and one to iterate (from 1 to N) down the "type tree".
This method also improves on the previous in that when a type T has
been deduced using BOOST_TYPEOF, the type is reused when BOOST_TYPEOF
is used again.
Anyhow, I have also implemented a feature for improving on the 64
template depth restriction. Haven't got access to an EDG based
compiler, but the implementation worked fine with VC 6.5

I have also looked at the newes implementation of your integral
encoding, Arkadiy, and it is basically the same as I am doing. I use
one value to encode an integer, with the exception of 0xffffffff and
0xfffffffe, but the side effect is that I can not use arrays to create
a size for sizeof. I have to use a struct containing two arrays, and I
don't know if this is as portable, so I should perhaps adapt to your
way of doing it.

Also, your version of TYPEOF_REGISTER_TEMPLATE_X differs from mine.
Where I use 
TYPEOF_REGISTER_TEMPLATE(some_class,2,(typename,unsigned int)), you use
TYPEOF_REGISTER_TEMPLATE_X(some_class,(typename)(unsigned int))

My has the advantage of looking more like a template argument list.
Your has the advantage of not having to specify the number of template
arguments...

Which one is best?

I haven't had time to do any work on integrating the two solutions
yet, my typeof implementation is not mature enough, I guess, as I
haven't tested it against any other unfortunate compilers without
partial template specialization support. Help on this would be greatly
appreciated.

--
Peder Holt
http://groups.yahoo.com/group/boost/files/typeof_fast.zip