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module XMonadContrib.ReadMap () where
{- An instance of Read for Data.Map.Map's; useful for people that are still
- compiling under 6.4. To use it, add the following line to StackSet.hs:
- import XMonadContrib.ReadMap
-}
import Data.Map (Map, fromList)
import GHC.Read
instance (Ord k, Read k, Read e) => Read (Map k e) where
readsPrec _ = \s1 -> do
("{", s2) <- lex s1
(xs, s3) <- readPairs s2
("}", s4) <- lex s3
return (fromList xs, s4)
-- parses a pair of things with the syntax a:=b
-- stolen from the GHC 6.6 sources
readPair :: (Read a, Read b) => ReadS (a,b)
readPair s = do (a, ct1) <- reads s
(":=", ct2) <- lex ct1
(b, ct3) <- reads ct2
return ((a,b), ct3)
readPairs :: (Read a, Read b) => ReadS [(a,b)]
readPairs s1 = case readPair s1 of
[(p, s2)] -> case s2 of
(',':s3) -> do
(ps, s4) <- readPairs s3
return (p:ps, s4)
_ -> [([p], s2)]
_ -> [([],s1)]
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