Boost logo

Boost :

From: John Femiani (JOHN.FEMIANI_at_[hidden])
Date: 2008-05-10 09:24:38


Bruno wrote:
...
>
> Yep precisely because the concept literally says "there must
> exist a specialization of point_traits with X such that this
> code is valid".
> It's finally as much a "point traits concept" as a "point concept".
> Maybe it would be better to have X being the specialized point_traits?
> It would require an additional point_type typedef in the
> point traits and would give something like:
>
> template <class X> // X is a point_traits struct PointTraits {
> typedef typename X::coordinate_type ctype;
> enum { ccount = X::coordinate_count };
>
> template <int I, int Count>
> struct dimension_checker
> {
> static void check()
> {
> const typename PT::point_type* point;
> ctype coord = X::template get<I>(*point);
> typename PT::point_type* point2;
> X::template get<I>(*point2) = coord;
>
> dimension_checker<I+1, Count>::check();
> }
> };
>
> template <int Count>
> struct dimension_checker<Count, Count>
> {
> static void check() {}
> };
>
> BOOST_CONCEPT_USAGE(Point)
> {
> dimension_checker<0, ccount>::check();
> }
> };
>
> Then, requirements inside algorithms would be done this way:
>
> template <class P>
> BOOST_CONCEPT_REQUIRES(
> ((PointTraits<point_traits<P> >)),
> (void))
> function_requiring_a_point(const P& p)
> {}
>

Well, if we agree that traits at least have the _potential_ to cause an
issue then why make the approach _more_traits based?

> It doesn't sound clearer to me though... If it's not what you
> were expecting, could you propose another concept definition?
>

I like most of what you have, and I am trying to get you guys to do the
thinking so I dont have to ;)

I'll work something up and send a link when I get a chance, but I think
that it will take some work and testing.

-- John


Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk