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Fri, 10 Jul 2015 11:18:05 GMT

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Fri, 10 Jul 2015 13:20:21 GMT

Ok after some code exploration I think that problem comes from :

template
    <
        typename CoordinateType,
        typename PromotedType,
        typename P1,
        typename P2,
        typename P,
        typename EpsPolicy
    >
static inline
PromotedType side_value(P1 const& p1, P2 const& p2, P const& p, EpsPolicy & eps_policy)
{
        CoordinateType const x = get<0>(p);
        CoordinateType const y = get<1>(p);
        CoordinateType const sx1 = get<0>(p1);
        CoordinateType const sy1 = get<1>(p1);
        CoordinateType const sx2 = get<0>(p2);
        CoordinateType const sy2 = get<1>(p2);
        PromotedType const dx = sx2 - sx1;
        PromotedType const dy = sy2 - sy1;
        PromotedType const dpx = x - sx1;
        PromotedType const dpy = y - sy1;
        eps_policy = EpsPolicy(dx, dy, dpx, dpy);
        return geometry::detail::determinant<PromotedType>
                (
                    dx, dy,
                    dpx, dpy
                );
    }

in file boost/geometry/trategies/cartesian/side_by_triangle.hpp

In my case :

CoordinateType = unsigned int
PromotedType = double

So, for example, on line

PromotedType const dpy = y - sy1;

a case where y < sy1 will lead to wrong result. A simple cast of y to PromotedType like

PromotedType const dpy = PromotedType (y) - sy1;

should in my case solve the problem.

If my understanding is good, PromotedType will be the most precise type between double and CoordinateType. So if I use input unsigned int 64, a similar error can happen and my correction will fail...

anonymous — Wed, 18 Nov 2015 11:06:12 GMT

Hi,

I just come to the news, will that bug be planned for correction ?

Regards, Eric Noirfalise

Boost C++ Libraries: Ticket #11470: Invalid results using convex_hull with unsigned integer points coordinates

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