[GRASS-user] no v.overlay with empty map: bug or feature?

[Patrice Dumas]

Hello,

With grass 6.4 I could do a v.overlay with an empty map.  That was in a 
loop to overlay different maps, so I thought I could start from an empty
map, and then overlay tables one at a time and process the result to 
remove unneeded columns and rename them.

With grass 7 (svn from yesterday) it doesn't seem to work anymore:

v.in.ascii -e output=empty_map input=-
v.in.region output=other_map
v.overlay ainput=empty_map binput=other_map output=maps_overlay operator=or

Copying vector features from <empty_map at PERMANENT>...
ERROR :No area features found in vector map <empty_map at PERMANENT>. Verify
        'atype' parameter.






I can try the other way around, after adding a table to other_map, same error:

v.db.addtable other_map
v.overlay ainput=other_map binput=empty_map output=maps_overlay operator=or

Copying vector features from <other_map at PERMANENT>...
 100%
Copying vector features from <empty_map at PERMANENT>...
ERROR :No area features found in vector map <empty_map at PERMANENT>. Verify
        'btype' parameter.



I already have a workaround, and I can see the point of the error message.
Yet, I am not completly sure that overlaying with an empty map should never
be possible.

Is it a bug, or is it on purpose?  If it is a bug I will report it in the
tracker, but I am not sure it is indeed a bug.

-- 
Pat