[Gretl-users] diagcat

Good morning, I just noticed the new (?) function diagcat() with the following help text: "Returns the direct sum of A and B, that is a block-diagonal matrix holding A in its north-west corner and B in its south-east corner. " Why would that be a _sum_? Also, what happens if A and B are not square? (I know, I could just try that out, but too lazy, and that wouldn't necessarily answer what's intended as a result.) And while I'm at it: I also noticed trimr() which trims rows. Don't know whether that's new, but why introduce a special function for this operation, couldn't it always be easily done by indexing, as in M[ttop+1:rows(M)-tbot] ? cheers, sven