module Calculator.Parser.Base where

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import           Control.Applicative           ((<$>))
import           Control.Monad                 (liftM2)
import           Text.ParserCombinators.Parsec

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parseNumber :: Parser Double
parseNumber = read <$> do
  neg <- optionMaybe (char '-')
  dec <- many1 digit
  flt <- option "" (liftM2 (:) (char '.') (many1 digit))
  return $ let num = dec ++ flt
           in maybe num (:num) neg

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parseId :: Parser String
parseId = liftM2 (:) letter (many (letter <|> digit))

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