    -- | This module provides default values for many types.
    --   To use the default value simply write 'def'.
    module System.Console.CmdArgs.Default where

    import Data.Int
    import Data.Word

    -- | Class for default values.
    class Default a where
        -- | Provide a default value, such as @()@, @False@, @0@, @[]@, @Nothing@.
        def :: a

    instance Default () where def = ()
    instance Default Bool where def = False
    instance Default Int where def = 0
    instance Default Integer where def = 0
    instance Default Float where def = 0
    instance Default Double where def = 0
    instance Default [a] where def = []
    instance Default (Maybe a) where def = Nothing

    instance Default Int8 where def = 0
    instance Default Int16 where def = 0
    instance Default Int32 where def = 0
    instance Default Int64 where def = 0
    instance Default Word where def = 0
    instance Default Word8 where def = 0
    instance Default Word16 where def = 0
    instance Default Word32 where def = 0
    instance Default Word64 where def = 0

    -- EXPANDY: $(2\10 instance ($(1,$ Default a$)) => Default ($(1,$ a$)) where def = ($(1,$ def)))
    instance (Default a1,Default a2) => Default (a1,a2) where def = (def,def)
    instance (Default a1,Default a2,Default a3) => Default (a1,a2,a3) where def = (def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4) => Default (a1,a2,a3,a4) where def = (def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5) => Default (a1,a2,a3,a4,a5) where def = (def,def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5,Default a6) => Default (a1,a2,a3,a4,a5,a6) where def = (def,def,def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5,Default a6,Default a7) => Default (a1,a2,a3,a4,a5,a6,a7) where def = (def,def,def,def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5,Default a6,Default a7,Default a8) => Default (a1,a2,a3,a4,a5,a6,a7,a8) where def = (def,def,def,def,def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5,Default a6,Default a7,Default a8,Default a9) => Default (a1,a2,a3,a4,a5,a6,a7,a8,a9) where def = (def,def,def,def,def,def,def,def,def)
    instance (Default a1,Default a2,Default a3,Default a4,Default a5,Default a6,Default a7,Default a8,Default a9,Default a10) => Default (a1,a2,a3,a4,a5,a6,a7,a8,a9,a10) where def = (def,def,def,def,def,def,def,def,def,def)