symantic/Language/Symantic/Interpreting/Eval.hs

   1 -- | Interpreter to evaluate a term as a host-term.
   2 module Language.Symantic.Interpreting.Eval where
   3
   4 import Control.Monad
   5
   6 -- * Type 'Eval'
   7
   8 -- | Interpreter's data.
   9 newtype Eval a = Eval { unEval :: a }
  10 instance Functor Eval where
  11         fmap f (Eval a) = Eval (f a)
  12 instance Applicative Eval where
  13         pure = Eval
  14         (Eval f) <*> (Eval a) = Eval (f a)
  15 instance Monad Eval where
  16         return = Eval
  17         (Eval a) >>= f = f a
  18
  19 -- | Interpreter.
  20 eval :: Eval a -> a
  21 eval = unEval
  22
  23 -- ** Constructors
  24 eval0 :: a -> Eval a
  25 eval0 = Eval
  26
  27 eval1 :: (a -> b) -> Eval a -> Eval b
  28 eval1 = liftM
  29
  30 eval2 :: (a -> b -> c) -> Eval a -> Eval b -> Eval c
  31 eval2 = liftM2
  32
  33 eval3 :: (a -> b -> c -> d) -> Eval a -> Eval b -> Eval c -> Eval d
  34 eval3 = liftM3