Geometry Boost List: [geometry] segment_ratio<__int64> causes a real number value corruption in boost::geometry::difference()

Subject: [geometry] segment_ratio<__int64> causes a real number value corruption in boost::geometry::difference()
From: sonic (mike.vasiljevs_at_[hidden])
Date: 2015-04-01 17:13:28

To make the story short double value 

"*1.3999999999999999*"

gets converted into

"*1.4000000000000057*"

when calling /boost::geometry::difference()/ on two polygons. Polygons were
defined in a standard way, that is:

/BOOST_GEOMETRY_REGISTER_C_ARRAY_CS(cs::cartesian)
BOOST_GEOMETRY_REGISTER_BOOST_ARRAY_CS(cs::cartesian)
BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)

typedef boost::geometry::model::d2::point_xy<double> point_xy;
typedef boost::geometry::model::polygon<point_xy > polygon;/

I found (after 2.5 hours being lost in the haunted template forest :p) that
the culprit is the following code (or I am d hing terribly wrong):

/        set<0>(point, boost::numeric_cast<coordinate_type>(
                get<0, 0>(segment)
                    + ratio.numerator() * dx / ratio.denominator()));/
                                        
in:

function:
/boost::geometry::policies::relate::segments_intersection_points::assign(..)/
location: /boost\geometry\policies\relate\intersection_points.hpp/
                                        
Which curiously enough means that value was stored/manipulated NOT a
*double* but as a /*rational number*/!

Were there any gobrutaly to handle this problem without having to bluntly
round off the values?

Would be happy to post an example if there are any answers to follow...

--------------
boost version: 1.56.0

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