I would like to support Sven's and Jack's views on this. It is really convenient to work with matrices with zero columns or rows. I agree that the number of rows should be same same for ~ and columns for |.

Andreas Noack Jensen

I think it would be a good thing if Gretl accepted zero dimension matrices more generally. For example, letting zeros(5,0)*zeros(0,5) return a 5x5 zero matrix and mols(mnormal(10,2),zeros(10,0),&res) return a zeros(0,2) matrix a overwrite res with the values from mnormal(10,2). It really works well in Matlab. It would simplify my code enormously as I could remove many if/else statements.

Best

Andreas Noack Jensen