Re: [boost] [Polygon] What does this error mean?

Subject: Re: [boost] [Polygon] What does this error mean?
From: Simonson, Lucanus J (lucanus.j.simonson_at_[hidden])
Date: 2009-09-01 16:56:53

Phil Endecott wrote:
> Dear Luke (& others),
> 
> Here's some test code, followed by the errors that I get when I try to
> compile it.  It boils down to some confusion about whether set is a
> type or a function.  Am I doing something that isn't allowed?  Thanks
> for any suggestions.
>
> template <>
> struct rectangle_traits<screen_box_t> {
>    typedef screen_coord_t coordinate_type;
>    typedef std::pair<screen_coord_t,screen_coord_t> interval_type;
>    static inline interval_type get(const screen_box_t& rectangle,
> orientation_2d orient) {
>      return (orient==HORIZONTAL) ?                              
>    std::make_pair(rectangle.x0,rectangle.x1) :
> std::make_pair(rectangle.y0,rectangle.y1); } };
> }; };

Phil,

I boils down to the fact that you are using std::pair<int, int> for your interval return type in get() in the screen_box_t traits, but did not register it as a type of interval concept or define traits for it.  If you set up the interval_traits for std::pair and register it with a specialization of geometry_concept for interval_concept you should be fine.  It states in the docs that while pair or tuple can be made concepts of point or interval, I don't do that for you because I can't make them simultaneously point and interval.  If you later set up point_traits for std::pair somewhere else you will get a raft of ambiguous overload errors because both point and interval interfaces will match your type.

Thanks,
Luke