#13368: Derive superclasses automatically if possible -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature request | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: wontfix | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #10607 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by songzh): I added a module `Data.Derive.Superclass` in derive- package[http://hackage.haskell.org/package/derive-topdown-0.0.2.0 which partially solve this problem. {{{ #!div style="font-size: 80%" {{{#!haskell
newtype IO_ a = IO_ (IO a) strategy_deriving_superclasses newtype_ ''MonadIO ''IO_
You will get:
strategy_deriving_superclasses newtype_ ''MonadIO ''IO_ ======> deriving newtype instance MonadIO IO_ deriving newtype instance Monad IO_ deriving newtype instance Applicative IO_ deriving newtype instance Functor IO_
Appearently, Functor f => Applicative f => Monad f => MonadIO f
newtype F32 = F32 Float newtype_deriving_superclasses ''RealFloat ''F32
You will get:
newtype_deriving_superclasses ''RealFloat ''F32 ======> deriving newtype instance RealFloat F32 deriving newtype instance RealFrac F32 deriving newtype instance Real F32 deriving newtype instance Num F32 deriving newtype instance Ord F32 deriving newtype instance Eq F32 deriving newtype instance Fractional F32 deriving newtype instance Floating F32 }}} }}}
Please try the package, if there are problem with it, please contact with me. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13368#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler