[GRASS-user] Vector map area statistics

[Vincent Godard]

Dear Grass users,
I have a simple problem for which there is probably a trivial solution or even 
a dedicated Grass function by I haven't been able to find it yet.
I am working in area for which I have a vector map of the bedrock geology and 
another vector map with a larger number of small basins. For each of these 
basins I would like to know the area (or percentage of the total basin area) 
that is occupied by the different geological units, and directly upload this 
result in the attribute table of the basins vector map (one column for each 
geological unit giving its area inside the basin or percentage).
Is there a simple way to do that with Grass?
Thanks in advance,
Vincent