AMDG On 05/22/2011 04:58 PM, Matt Calabrese wrote:
On Sun, May 22, 2011 at 7:27 PM, Steven Watanabe <watanabesj@gmail.com>wrote:
Thanks. It would be awesome if we could integrate this with your Generic library, so a single concept definition is sufficient for both.
Yeah, that would be amazing. I bet we could get something workable with simple concepts in not too much time, though right now I have other priorities for the library (I want to first get all of the concepts of N2914 working and tested). The complicated parts of applying type erasure here that I can think of are with associated types -- for instance, a type-erased container should probably automatically be working with type-erased iterators, right? So handling things correctly implies my library figuring out all of the constraints that affect an associated type in any way, which could be tricky, as constraints can be scattered around the encapsulating concept. While I can check the constraints fine, at a high level I don't really know which constraints affect which types, whether directly or indirectly, if you get what I'm saying.
Yeah. I don't really have a good way to handle associated types at all. I suspect that the way I'm using placeholders will interact badly with associated types in your macros.
All I know is whether a given constraint is satisfied or not, but it's difficult to determine exactly which associated types are affected by which constraints since they can be referenced in any kind of arbitrary type expression.
If the constraint is of the form SomeConcept<A, B, C>, I can use placeholders for the arguments, and pick it apart with TMP.
Anyway, this would be awesome to accomplish, especially if we could figure out a way to handle the general case, though, at least at my end, it's a ways off. I feel like Sean Parent talked a little bit about similar functionality with Poly. I'll check it out and try to keep all of this somewhere in my mind as I make further progress with the Generic library.
In Christ, Steven Watanabe