import RefactoredParser

-- the expression datatype
data Expr
  = Num Int
  | Add Expr Expr
  | Mul Expr Expr
 deriving ( Show, Eq )
 


num, expr, term, factor :: Parser Expr

num    = pmap Num number
expr   = chain term   '+' Add
term   = chain factor '*' Mul
factor = char '(' >-> expr <-<  char ')'  
      +++ num


readExpr :: String -> Maybe Expr
readExpr = topLevel expr