Edit Question - KnowledgeHub

Title Body

I have a few nested records that I need to validate, and I wonder what is an idiomatic Haskell way to do it. To simplify: data Record = Record { recordItemsA :: [ItemA], recordItemB :: ItemB } deriving (Show) data ItemA { itemAItemsC :: [ItemC] } deriving (Show) Requirements are: Collect and return all validation errors Some validations may be across items, e.g. ItemsA against ItemB String s are sufficient to represent errors I currently have code that feels awkward: type ErrorMsg = String validate :: Record -> [ErrorMsg] validate record = recordValidations ++ itemAValidations ++ itemBValidations where recordValidations :: [ErrorMsg] recordValidations = ensure (...) $ "Invalid combination: " ++ (show $ recordItemsA record) ++ " and " ++ (show $ recordItemsB record) itemAValidations :: [ErrorMsg] itemAValidations = concat $ map validateItemA $ recordItemsA record validateItemA :: ItemA -> [ErrorMsg] validateItemA itemA = ensure (...) $ "Invalid itemA: " ++ (show itemA) itemBValidations :: [ErrorMsg] itemBValidations = validateItemB $ recordItemB record validateItemB :: ItemB -> [ErroMsg] validateItemB itemB = ensure (...) $ "Invalid itemB: " ++ (show itemB) ensure :: Bool -> ErrorMsg -> [ErrorMsg] ensure b msg = if b then [] else [msg]

Tags (comma-separated) Cancel