Hi again, not sure if we discussed this before (probably we did): It might be useful to allow an empty matrix {} as a default argument for a matrix, instead of "null". Background/example: <pseudo-hansl> function void cm(matrix m[null]) # call to backend function defined elsewhere: if exists(m) mybackend(m) # impossible if exists(m)==0 else mybackend(null) endif end function </pseudo-hansl> This if-else-endif construction would be unnecessary if we could just pass around empty matrices as arguments. And instead of the check exists(m) we could simply use nelem(m) to see what we got. But I vaguely remember that Allin had some technical objections at the C level... thanks, sven