Ast.hs

-- bound
import Bound

-- | Standalone type for 'let' bindings.
data Lets f v = Lets (f v) (Scope () f v)
     
instance Bound Lets where
         Lets l b >>>= f = Lets (l >>= f) (b >>>= f)

-- | Abstract syntax trees with optional extra types involved.
data Abstract l v
     = Free v                              -- ^ Free variables.
     | With (l (Abstract l) v)             -- ^ Other types.
     | Apply (Abstract l v) (Abstract l v) -- ^ Function application.

instance Bound l => Monad (Abstract l) where
         return = Free
         Free v >>= f = f v
         With l >>= f = With (l >>>= f)
         Apply a b >>= f = Apply (a >>= f) (b >>= f)