On Thu, Dec 8, 2011 at 6:55 PM, Paul Monday <paul.monday at parsci.com> wrote: > data UMatrix a = UMatrix (V.Vector (U.Vector a)) > deriving (Show, Eq) Note that you may also use something like data UMatrix a = UMatrix !Int !(U.Vector a) where the Int is the number of columns. Cheers, -- Felipe.