18 lines
473 B
Haskell
18 lines
473 B
Haskell
|
module XMonad.Configurable (Configurable, EndoM(..), configure) where
|
||
|
|
|
||
|
|
import Control.Monad ((<=<))
|
||
|
|
import Control.Monad.Reader
|
||
|
|
|
||
|
|
newtype EndoM m a = EndoM { appEndoM :: a -> m a }
|
||
|
|
|
||
|
|
instance Monad m => Semigroup (EndoM m a) where
|
||
|
|
EndoM f <> EndoM g = EndoM (f <=< g)
|
||
|
|
|
||
|
|
instance Monad m => Monoid (EndoM m a) where
|
||
|
|
mempty = EndoM pure
|
||
|
|
|
||
|
|
type Configurable a = EndoM (Reader a) a
|
||
|
|
|
||
|
|
configure :: Configurable a -> a
|
||
|
|
configure (EndoM f) = fix (\self -> runReader (f self) self)
|