module Expr1Simple where
import UU_Parsing

instance Symbol Char

pDigit = (\d -> ord d - ord '0') <$> pAnyOf ['0'..'9']

pNat = foldl (\a b -> a*10 + b) 0 <$> pSome pDigit

pParens = pPacked (pSym '(') (pSym ')')

pFact =   pNat
      <|> pParens pExpr

pTerm = pChainl (   (*) <$ pSym '*'
                <|> div <$ pSym '/'
                )
                pFact

pExpr = pChainl (   (+) <$ pSym '+'
                <|> (-) <$ pSym '-'
                )
                pTerm

t p inp = let (r, rest, errors) = parse p null inp
          in do putStr (show r)
                putStr (show errors) 

t1 = t pExpr "3*4-6"
t2 = t pExpr "3**4-6"

main :: IO ()
main      = do putStr "Enter expression: "
               inp <- getLine
               let (r, rest, errors) = parse pExpr null inp
               putStr (show r)
               putStr (show errors)               
               main