At Tue, 28 Sep 2010 18:45:23 +0100, Mathias Gaunard wrote:
On 28/09/10 18:33, David Abrahams wrote:
At Tue, 28 Sep 2010 10:00:54 -0500, Andrew Sutton wrote:
It seems to me that writing constraints in terms of valid expressions gives you flexibility when you want it, but doesn't preclude the strengthening of requirements when needed.
It's not that there's anything you *can't* express with valid expressions, it's that they're difficult to use correctly, and the most natural way of using them creates a big mess for algorithm writers. Furthermore, they don't offer any compelling value over the alternative.
Please demonstrate how you check that a type models a concept without using a set of valid expressions to define the concept, but only with signatures
See the implementation of ConceptGCC. There's a demonstration in working code. But...
in an archetype-like fashion.
...the whole sentence became meaningless to me when you added "in an archetype-like fashion." I have no idea what it means, and it seems incongruous to bring up archetypes in the context of a discussion of the mechanics of checking conformance of a type to a concept. -- Dave Abrahams BoostPro Computing http://www.boostpro.com