// Mart Lubbers s4109503, Camil Staps s4498062

definition module RefactorX

from StdClass import class toString
import StdEnv

:: Expr = NR Int | VAR Name | OP Expr Operator Expr | LET Name Expr Expr
:: Name :== String
:: Operator = PLUS | MIN | MUL | DIV
:: Val = Result Int | Undef


instance toString Expr
free :: Expr -> [Name]
remove_unused_lets :: Expr -> Expr
eval :: Expr -> Val