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