[geos-devel] C API coordinate sequence dimensions

[Martin Davis]

Actually JTS implements this correctly.  The return value from 
getDimension is computed by the implementation of CoordinateSequence.  
In the case of DefaultCoordinateSequence (which by the way is deprecated 
and replaced by CoordinateArraySequence) the value is alway 3, since the 
Coordinate representation used by these sequences always allows for 3 
ordinates.

In the case of PackedCoordinateSequence the dimension can be selected on 
creation, and this is the value that is returned by getDimension.

Sanak wrote:
> Hi list,
>
> I don't know that this is a known bug, but 
> CoordinateArraySequence.getDimension() method always return 3.
>
> [trunk/source/headers/geos/geom/CoordinateArraySequence.h - line 88]
> size_t getDimension() const { return 3; }
>
>
> JTS(JTS Topology Suite) seems to be also the same.
>
> [jts/src/com/vividsolutions/jts/geom/DefaultCoordinateSequence.java - 
> line 95]
> public int getDimension() { return 3; }
>
> I don't know that this is a specification or not...
>
> Regards,
>
> Sanak.
>
> 2009/1/12 Sean Gillies <sgillies at frii.com <mailto:sgillies at frii.com>>
>
>     I'm finding that GEOSCoordSeq_getDimensions returns 3 no matter what
>
>      # Accessing libgeos_c via Python ctypes
>      >>> s = lgeos.GEOSCoordSeq_create(2, 2)
>      >>> ndim = c_int()
>      >>> lgeos.GEOSCoordSeq_getDimensions(s, byref(ndim))
>      1
>      >>> ndim
>      c_long(3)
>
>     Is this a known bug? Looks like we're only testing creation of 3D
>     coordinate sequences in
>
>     http://trac.osgeo.org/geos/browser/trunk/tests/unit/capi/GEOSCoordSeqTest.cpp
>
>     --
>     Sean Gillies
>     http://sgillies.net
>
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-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022