Quiet

Generic deriving of Read / Show with no record labels.

Often one wants to create a newtype which has a convenient field accessor like unUserId below, but that unfortunately makes the Show instance which is derived overly verbose.

For example:

newtype UserId = UserId { unUserId :: String }
  deriving (Read, Show)

>>> show (UserId "simon")UserId {unUserId = "simon"}>>> read "UserId {unUserId = \"simon\"}" :: UserIdUserId {unUserId = "simon"}

With DerivingVia Quiet you can have a Show instance which doesn't print the field labels. It will render as if the unUserId accessor wasn't present at all.

newtype UserId = UserId { unUserId :: String }
  deriving (Generic)
  deriving (Read, Show) via (Quiet UserId)

>>> show (UserId "simon")UserId "simon">>> read "UserId \"simon\"" :: UserIdUserId "simon"

If you want to derive Read / Show without using DerivingVia then you can use qreadPrec and qshowsPrec directly.

instance Read UserId where readPrec = qreadPrec
instance Show UserId where showsPrec = qshowsPrec