Geometry Boost List: [geometry] difference algorithm yields invalid multi-polygon

Subject: [geometry] difference algorithm yields invalid multi-polygon
From: Volker Schöch (vschoech_at_[hidden])
Date: 2014-11-17 11:24:05

polygonA = MULTIPOLYGON(((1701 985,3501 985,3501 2785,1701 2785,1701 985)))
polygonB = MULTIPOLYGON(((1698 1860,1698 1122,2598 1392,3492 1842,3492 32706,2598 2340,1698 1860)))

difference(polygonA, polygonB, polygonC)
-> polygonC == MULTIPOLYGON(((1701 1122,1701 985,3501 985,3501 2785,3492 1857,3492 1842,2598 1392,1701 1122)),((1701 1861,2598 2340,1669 2785,1701 2785,1701 1861)))

Both, polygonA and polygonB, satisfy is_valid(...), but polygonC doesn't.
Is there anything wrong with the input? Is this a bug?

Regards
   Volker

--
Volker Schöch | vschoech_at_[hidden]<mailto:vschoech_at_[hidden]>
Senior Software Engineer
We are looking for C++ Developers: http://www.think-cell.com/career
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