[geos-devel] BUG: relate(g1,g2) crashes with GEOMETRYCOLLECTION?

[Paul Ramsey]

Enlighten me: how would relate on a geometrycollection differ from 
relate on a multipolygon? Don't most of the tests collapse to an or() 
of the results of each test performed individually on the collection 
components?

overlaps (gc(A,B),gc(C,D)) = 
or(overlaps(A,C),overlaps(A,D),overlaps(B,C),overlaps(B,D))

P.

On Tuesday, April 8, 2003, at 01:42 PM, David Blasby wrote:

> Martin Davis wrote:
>
>> Yep.  Neither GEOS nor JTS support GeometryCollections as arguments 
>> to relate.  This is partly because the semantics aren't very well 
>> defined, and partly because the obvious semantics [ X.relate(GC) = 
>> X.relate(union(GC.components) ] would make the operation non-robust.
>>
>> That said, we or you could always implement the above semantics 
>> fairly easily...
>>
> Its unfortunate that the spec doesnt tell you what to do in the case 
> of GEOMETRYCOLLECTIONs.
>
> I've also noticed that overlaps(g,g) is FALSE!
>
> dave
>
>
>
>
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      Paul Ramsey
      Refractions Research
      Email: pramsey at refractions.net
      Phone: (250) 885-0632