Le 22/05/14 18:23, paul Fultz a écrit :
Hi,
I developed a trait introspection library for C++14 based on Eric Niebler's concept checking, here:
https://github.com/pfultz2/Tick
So you can build a simple `is_incrementable` trait like this:
TICK_TRAIT(is_incrementable) { template<class T> auto requires(T&& x) -> TICK_VALID( x++, ++x ); };
Then use it like this:
static_assert(is_incrementable<T>(), "Not incrementable");
Also, you can validate the return of an expressions like this:
TICK_TRAIT(is_equality_comparable) { template<class T, class U> auto requires(T&& x, U&& y) -> TICK_VALID( returns<bool>(x == y), returns<bool>(x != y) ); };
You can also match against another trait using placeholder expressions:
TICK_TRAIT(is_incrementable) { template<class T> auto requires(T&& x) -> TICK_VALID( return<std::is_integral<_>>(x++), return<std::is_integral<_>>(++x) ); };
Any feedback would be appreciated. Also, I don't knw if there would be any interest in incorporating this into boost.
I recommend that you do not use identifiers 'concept' or 'requires'. They are likely to become keywords in C++17. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4040.pdf. If added, this will break your code and negatively surprise your users. Worse, if your library becomes popular, it may prevent the addition of the keywords, and C++ will have to resort to uglier names like "concept_def" and "concept_requires". Regards, 7rzej