Daniel Frey <daniel.frey@aixigo.de> writes:
Hm, sorry, this is my fault. I think I haven't posted an analysis *why* all approaches of typeof-emulation won't do for the constant library. I just thought about these things, taking into account the examples for unit-libraries, and decided it won't work. The reason is, that the author of the constant library (or the constants) cannot know which unit-libraries are to be supported, and the author of the unit-library doesn't want to register stuff for a specific constant library. Dependencies. The problem is, that you have to register operators for pairs of arguments, one from the unit library, the other from the constant-library.
I'm don't see why you'd need to register operators. If I'm not mistaken, with Arkadiy's solution you only need to register user-defined types and templates (and maybe functions if they are used as template arguments).
Who is supposed to do that? But I also remember that this was a problem anyway, as -depending on the design of the unit-library- it sometimes worked out-of-the-box, sometimes it didn't. I guess I will have to work this out more detailed, but currently, I don't have time for it...
And now you even say that it's OK to violate existing language rules on purpose just because you think it will likely work in practice? As an experiment, to see how portable it actually is... and only because we expect to see full language support soon.
Oh, I missed the "full language support soon"-part. Again, sorry.
IMO __typeof__ is an option as long as there's a fallback for compilers that don't support it.
As an alternative: Would a limited functionality be OK, too? In my case, meaning you can use the constant library with all types that have the same result type for operators as their arguments, e.g. T+T gives you a T, etc.
It seems reasonable that a library acquires added features on compilers where language extensions are available.
This doesn't hold for unit-types, where we need typeof instead of the simple assumption above, but it still provides lots of useful functionality for "normal" types.
Seems OK to me, in principle. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com