Hi. I have an array (Data.Array.Vector.UArr) of Word8 elements. Elements are stored as Word8 to keep memory usage down. Now I need to compute the sum of all the array elements; what is the best method? The sum must be of type Int. How efficient is to simply convert to an UArr Int, using: mapU fromIntegral v :: UArr Int ? What about, instead, of something like: genericSumU :: (UA e, Integral e) => UArr e -> Int genericSumU = foldU add 0 where add x y = x + fromIntegral y ? Unfortunately the latter does not compile: Couldn't match expected type `Int' against inferred type `e' `e' is a rigid type variable bound by the type signature for `genericSumU' at bin/process-data-1.hs:64:19 In the expression: foldU add 0 In the definition of `genericSumU': genericSumU = foldU add 0 where add x y = x + fromIntegral y Moreover, this is not really a generic version. I would like to have: genericSumU :: (Num i, UA e, Num e) => UArr e -> i is this possible? Thanks Manlio