Not having participated in haskell' before, I'm not sure how to put these perfecting amendments--mot langauge changes--into the pot. Doug McIlroy The specification of List.transpose does not tell what a "column" of a ragged-right list of rows is, either directly or by example. Here is a fuller spec, plus some properties. ----------------------------------------------------- A generalization of the customary matrix operation, transpose returns a list of columns extracted from a list of rows. The jth column of x::[[a]] comprises all extant elements x!!i!!j ordered by i. In the subdomain of list structures that have positive nonincreasing row lengths, e.g. matrices and Young tableaux, transpose . transpose === id (transpose x) !! i !! j === x !! j !! i In general transpose . transpose . transpose === transpose sum . map length . transpose === sum . map length Example: transpose [[10,11],[20],[],[30,31,32]] === [[10,20,30],[11,31],[32]] ----------------------------------------------------- The reference definition can be simplified: transpose xss = case [h | (h:_) <- xss] of [] -> [] hs -> hs : transpose [tss | (_:tss) <- xss]