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{- attoparsec utility functions
-
- Copyright 2019 Joey Hess <id@joeyh.name>
- Copyright 2007-2015 Bryan O'Sullivan
-
- License: BSD-3-clause
-}
module Utility.Attoparsec where
import qualified Data.Attoparsec.ByteString as A
import qualified Data.ByteString as B
-- | Parse and decode an unsigned octal number.
--
-- This parser does not accept a leading @\"0o\"@ string.
octal :: Integral a => A.Parser a
octal = B.foldl' step 0 `fmap` A.takeWhile1 isOctDigit
where
isOctDigit w = w >= 48 && w <= 55
step a w = a * 8 + fromIntegral (w - 48)
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