On Sun, Sep 16, 2012 at 6:31 PM, Dave Abrahams <dave@boostpro.com> wrote:
on Mon Sep 03 2012, Andrzej Krzemienski <akrzemi1-AT-gmail.com> wrote:
I do not know if Boost.ConceptCheck offers the capability of verifying any boolean predicate.
Sure; even if the concept isn't already in the library, you can easily write it.
So if we can program a static boolean predicate then we can program a ConceptCheck concept that will statically assert it and make it fail at compile-time. I guess however that the opposite is not true. There are conditions that can be programmed to generate a hard compiler failure (e.g., using ConceptCheck) but we cannot create a boolean meta-function for them (e.g., to use enable-if and/or SFINAE-like concepts). For example we can program CopyConstructible but we cannot program has_copy_constructor--am I correct? Is that true with C++11 expression SFINAE as well? If that is the case, there can be type requirements that we can only program using hard-failing-concepts (ConceptCheck concepts within Contract's check clause) but not using SFINAE-concepts (possible future Boost.Contract's requires clause). Thanks, --Lorenzo