id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
10835	difference of multilinestring and polygon yields wrong result	Philipp Müller <pmueller@…>	Barend Gehrels	"I am using the following typedefs to simplify reading:

{{{
typedef boost::geometry::model::point<int,2,boost::geometry::cs::cartesian> TPoint;
typedef boost::geometry::model::linestring<TPoint> TLinestring;
typedef boost::geometry::model::multi_linestring<TLinestring> TMultiLinestring;
typedef boost::geometry::model::polygon<TPoint, /*ClockWise*/false, /*Closed*/false> TPolygon;
}}}

I have a multilinestring from which I want to subtract two polygons. 
The multilinestring and polygons are as follows

{{{
TMultiLinestring multilinestring; 
boost::geometry::read_wkt(""MULTILINESTRING((5239 2113,1020 2986))"", multilinestring);
TPolygon polygon1; 
boost::geometry::read_wkt(""POLYGON((5233 2113,5200 2205,1020 2205,1020 2022,5200 2022))"", polygon1);
TPolygon polygon2; 
boost::geometry::read_wkt(""POLYGON((5233 2986,5200 3078,1020 3078,1020 2895,5200 2895))"", polygon2);
}}}

First, I subtract polygon1 from multilinestring, which works fine:

{{{
TMultiLinestring multilinestringOut1;
boost::geometry::difference(multilinestring, polygon1, multilinestringOut1);
// works as expected: multilinestringOut1 holds MULTILINESTRING((5239 2113,5233 2114)(4795 2205, 1020 2986))
}}}

Now I want to subtract polygon2 from multilinestringOut1 (the intermediate result from the previous calculation), which yields a wrong result.


{{{
TMultiLinestring multilinestringOut2;
boost::geometry::difference(multilinestringOut1, polygon2, multilinestringOut2); 
// not   as expected: multilinestringOut2 holds MULTILINESTRING((5239 2113,5233,2114)(4795 2205, 5406 1580))
}}}

I would expect multilinestringOut2 to hold 

{{{
MULTILINESTRING((5239 2113,5233,2114)(4795 2205, 1460 2895))
}}}

"	Bugs	closed	Boost 1.58.0	geometry	Boost 1.57.0	Regression	fixed	geometry difference multi_linestring polygon	mkaravel