47 lines
1.3 KiB
Haskell
47 lines
1.3 KiB
Haskell
{- misc utility functions
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-
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- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Utility.Misc where
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import System.IO
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import System.IO.Error (try)
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import Control.Monad
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import Control.Applicative
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{- A version of hgetContents that is not lazy. Ensures file is
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- all read before it gets closed. -}
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hGetContentsStrict :: Handle -> IO String
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hGetContentsStrict = hGetContents >=> \s -> length s `seq` return s
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{- A version of readFile that is not lazy. -}
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readFileStrict :: FilePath -> IO String
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readFileStrict = readFile >=> \s -> length s `seq` return s
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{- Attempts to read a value from a String. -}
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readMaybe :: (Read a) => String -> Maybe a
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readMaybe s = case reads s of
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((x,_):_) -> Just x
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_ -> Nothing
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{- Catches IO errors and returns a Bool -}
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catchBoolIO :: IO Bool -> IO Bool
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catchBoolIO a = catchDefaultIO a False
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{- Catches IO errors and returns a Maybe -}
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catchMaybeIO :: IO a -> IO (Maybe a)
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catchMaybeIO a = catchDefaultIO (Just <$> a) Nothing
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{- Catches IO errors and returns a default value. -}
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catchDefaultIO :: IO a -> a -> IO a
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catchDefaultIO a def = catch a (const $ return def)
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{- Catches IO errors and returns the error message. -}
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catchMsgIO :: IO a -> IO (Either String a)
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catchMsgIO a = dispatch <$> try a
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where
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dispatch (Left e) = Left $ show e
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dispatch (Right v) = Right v
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