Hello everybody, When I compile a file containing ... plotAsString::(Integral a)=>[(a,a)]->a->String plotAsString locs ans = let xs = map fst locs ys = map snd locs locsmap = M.fromList (zip locs [0..]) bufsize=10 min' = ((\x -> x-bufsize) . minimum) max' = ((\x -> x+bufsize) . maximum) (bmin@(x0,y0),bmax@(x1,y1)) = ((min' xs,min' ys),(max' xs,max' ys)) plotString = foldl (\curStr newRowId -> (foldl (\ccStr newColId -> (ccStr++(case (M.member (newRowId,newColId) locsmap) of (Just v) -> ("." ++ (show v) ++ ".") (Nothing) -> " "))) curStr [y0..y1])) "" [x0..x1] in plotString I get the following error.. main.hs:34:107: Couldn't match expected type `Bool' with actual type `Maybe t0' In the pattern: Just v In a case alternative: (Just v) -> ("." ++ (show v) ++ ".") In the second argument of `(++)', namely `(case (M.member (newRowId, newColId) locsmap) of { (Just v) -> ("." ++ (show v) ++ ".") (Nothing) -> " " })' can somebody help? Thanks, Sunil.