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User.hs
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User.hs
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{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FunctionalDependencies, MultiParamTypeClasses, FlexibleInstances #-}
module User (
User (..)
, Admin (Admin)
, Ordinary (Ordinary)
, NewUser
, ReadUser
, UpdateUser
, newUser
, readUser
, updateUser
) where
data User id email color = User id email color
type NewUser color = User () (Maybe String) color
type ReadUser color = User Int (Maybe String) color
type UpdateUser color = User Int (Maybe (Maybe String)) (Maybe color)
data Admin = Admin
data Ordinary = Ordinary
data Color
class Secret rle field result | rle field -> result
instance Secret Admin Color String
instance Secret Ordinary a ()
readUser :: (Secret rle Color color) => rle -> Int -> IO (Maybe (ReadUser color))
readUser = undefined
updateUser :: (Secret rle Color color) => rle -> UpdateUser color -> IO (Maybe (ReadUser color))
updateUser = undefined
newUser :: (Secret rle Color color) => rle -> color -> Maybe String -> IO (NewUser color)
newUser = undefined