module VarType where {

{-
-- Monadic Version を試す時には必要
type M a = a;

unitM :: a -> M a;
unitM a = a;

bindM :: M a -> (a -> M b) -> M b;
m `bindM` k = k m;
-}

data Value = Num Double
             deriving (Eq, Show);

showValue (Num d) = show d;

type Decl = (String, Expr);
data Expr = Mult Expr Expr | Add Expr Expr | Const Value
          | Let Decl Expr {- Let [Decl] Expr -} | Var String  
            deriving (Eq, Show);

}