import Control.Exception
import Rpn

main = do
    putStrLn "\nEnter an expression:"
    line <- getLine      
    if null line          
    then return ()
    else do
        putStrLn ("RPN: " ++ (showFormulaRPN line)) `catch` handler
        putStrLn ("= " ++ (show (evaluateFormula line))) `catch` handler
        main

    where
        handler :: SomeException -> IO ()
        handler ex = putStrLn $ "Exception: " ++ show ex