flatten :: ByteString -> [ (String, Int, Int, String) ] flatten json = case decode json of Nothing -> [] -- Type inference here can infer that

flatten :: ByteString -> [ (String, Int, Int, String) ] flatten json = case decode json of Nothing -> [] -- Type inference here can infer that we're using `val` as -- :: HashMap String (HashMap String (HashMap String String)) Just val -> let books = ["Genesis", "Exodus" {- ...and so forth -} ] in [ (book, chNum, vsNum, verse) -- for every book in the list of books... | book <- books -- find the corresponding map , Just bookMap <- [HM.lookup book val] -- for every number in the range [1..max] for chapters , chNum <- [1..HM.size bookMap] -- pull that map out of the submap , Just chMap <- [HM.lookup (show chNum) bookMap] -- ...and for every number in the range [1..max] for verses , vsNum <- [1..HM.size chMap] -- ...pull the verse out of the sub-sub map , Just verse <- [HM.lookup (show vsNum) chMap] ] Okay, this isn't as type-safe or signed-in-triplicate as the supplied Haskell solution, but if we're comparing size-to-size, then this is pretty terse while also avoiding partial functions (the supplied Haskell solution uses read, which can throw an error if we happen to have a non-numeric key in the wrong place) and still working within the restrictions of what was given.