NumericExpr.hs

module NumericDSL
  where

---- Example GHCi session:
-- ghci> example (10 :: Int)
-- 130
-- ghci> example (10 :: Expr)
-- Mul (Add (Lit 10) (Lit 3)) (Lit 10)


example :: Num a => a -> a
example x = (x + 3) * x

data Expr
  = Lit Int
  | Add Expr Expr
  | Mul Expr Expr
  deriving (Show)

instance Num Expr where
  fromInteger x = Lit (fromInteger x)
  x + y = Add x y
  x * y = Mul x y