[boost] Re: Constrained genericity at last? (any interest in an operator traits/concept traits library?)

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2004-09-18 21:19:55

Hi Terje,

I had a look at your library proposal today.
Looks like a very valuable tool for everyone into generic programming.

It seems quite easy to add new concepts, which I think is one of the 
most important things (the has_member family looks very promising).

I was able to build the operator_traits test with GCC 3.2.3 mingw (about
20 minutes PIII,600MHz,512MB RAM - 100% passed - guess I just had to see
it with my own eyes ;+).
It failed to build on MSVC 13.10.3077 and Borland 5.4.6 (I kept the
output, in case you are interested).

It might be possible to put the prefiltering stage of the operator
traits into sort of table based form, making it easier to maintain,
eliminating a lot of inclusion dependencies and template instantiations
and covering tests for builtin operators (if they should be detected,
that is) as well.
This can probably be done with a technique in some way similar to the 
one applied to the operator checking itself - defining a rule set of 
overloaded functions to match the exclusions. Classes with a converting 
copy constructor can be used to categorize the types matched by the 
rules. The rule sets for different operator categories could be put into 
nested namespaces so inner categories could 'inherit' the rules of the 
outter ones.
I attached some experimental source code for the prefiltering of an 
operator+ check to clearify the basic idea (compiles with GCC and MSVC 
and CVS version of boost).

However, I am looking forward to using your library.
It's late here now - so that's it for today.

Best regards,

Tobias