On style, yes. A concrete example of what I asked before. The following doesn't type check for obvious reasons. In your opinion what is the most elegant way to fix it? Like I said, I'm starting to feel like defining my own operators is the way to go. On the other hand, this kind of situation seems quite common and there are no such operators in the standard libraries, so I might be wrong here. Opinions anyone? J.A. ------------------ Source Code: ------------------ module TypeCheck where import Data.Array import Data.Ix bigR :: Double bigR = sum[a!(i,j)*(r!i - n*b!i)*(r!j-n*b!j) | (i,j)<-range(bounds a)]/n a :: Array (Int,Int) Double b :: Array Int Double r :: Array Int Int n :: Int a=undefined b=undefined r=undefined n=undefined