{-# OPTIONS -Wall #-}
module RPN where

import Data.Char

data Token = DefineYourTokenConstructorsHere
  deriving (Show)

lexer :: String -> [Token]
lexer = error "implement me"

data Expr = DefineYourExprConstructorsHere
  deriving (Show)

parser :: [Token] -> Expr
parser = error "implement me using parser'"

parser' :: [Expr] -> [Token] -> Expr
parser' = error "implement me"

eval :: Expr -> Int
eval = error "implement me"