operation.hs

module Main where
  import Text.ParserCombinators.Parsec
  
  runop :: Char -> Integer -> Integer -> Integer
  runop '+' firstOperand secondOperand = firstOperand + secondOperand
  runop '-' firstOperand secondOperand = firstOperand - secondOperand
  runop '*' firstOperand secondOperand = firstOperand * secondOperand
  runop '^' firstOperand secondOperand = firstOperand ^ secondOperand

  operation :: Parser Integer
  operation = do
    firstOperand  <- number
    operationChar <- operator
    secondOperand <- number
    return (runop operationChar firstOperand secondOperand)

  operator :: Parser Char
  operator = do
    operatorToken <- oneOf "+-*^"
    return (operatorToken)

  number :: Parser Integer
  number = do
    numberToken <- many (oneOf "0123456789")
    return (read numberToken)