On Sep 27, 2010, at 9:51 AM, Andrew Sutton wrote:
I was never convinced that valid expressions are the wrong approach.
To convince yourself:
* Write down the find_if algorithm in a natural way * write down the valid expressions implied by that algorithm * now re-check the algorithm against the valid expressions
So, no takers? :-)
I'm not sure I fully understand the problem.
Of course not; you didn't try it! ;-)
Surely, you can use the Concept_check library to describe constraints for the find_if algorithm, and the Concept_check library internally validates those constraints against expressions expected to be valid. To me, that would imply that valid expressions can be used to describe constraints.
Am I missing something?
Among other things, you're missing the other half of concept checking: checking algorithm bodies against constraints (which is done in the Concept_check library by using archetypes). P.S. I'm not claiming concepts can't be described via valid expressions; I'm claiming it's the wrong approach, for reasons that should become evident to anyone who *actually does the exercise*. -- Dave Abrahams BoostPro Computing http://boostpro.com