tphyahoo:
> I was trying to follow the reasoning in Don's article on using haskell
> for shell scripting
>
> http://cgi.cse.unsw.edu.au/~dons/blog/2007/03/10
>
> In the source listing at the end we is
>
> newtype Shell a = Shell { runShell :: ErrorT String IO a }
> deriving (Functor, Monad, MonadIO)
>
> and I don't understand it what "deriving" is doing here, nor have I
> been able to find documentation on it.
That's 'cunning newtype deriving, my new favourite ghc language
extension.
http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html#newtype-deriving
We also use it in xmonad,
newtype X a = X (ReaderT XConf (StateT XState IO) a)
deriving (Functor, Monad, MonadIO, MonadState XState, MonadReader XConf)
:-)
-- Don
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