dbus-core-0.4: DBus/Util.lhs

% Copyright (C) 2009 John Millikin <jmillikin@gmail.com>
% 
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\clearpage
\section{Misc. utility functions}

\ignore{
\begin{code}
module DBus.Util
	( checkLength
	, parseMaybe
	, mkUnsafe
	, hexToInt
	, eitherToMaybe
	) where

import Text.Parsec (Parsec, parse)
import Data.Char (digitToInt)
\end{code}
}

\begin{code}
checkLength :: Int -> String -> Maybe String
checkLength length' s | length s <= length' = Just s
checkLength _ _ = Nothing
\end{code}

\begin{code}
parseMaybe :: Parsec String () a -> String -> Maybe a
parseMaybe p = either (const Nothing) Just . parse p ""
\end{code}

\begin{code}
mkUnsafe :: Show a => String -> (a -> Maybe b) -> a -> b
mkUnsafe label f x = case f x of
	Just x' -> x'
	Nothing -> error $ "Invalid " ++ label ++ ": " ++ show x
\end{code}

\begin{code}
hexToInt :: String -> Int
hexToInt = foldl ((+) . (16 *)) 0 . map digitToInt
\end{code}

\begin{code}
eitherToMaybe :: Either a b -> Maybe b
eitherToMaybe (Left  _) = Nothing
eitherToMaybe (Right x) = Just x
\end{code}