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{-# OPTIONS -fglasgow-exts #-}
module Runnable where
import Control.Monad
import Text.Read
import Text.ParserCombinators.ReadPrec
import Config (runnableTypes)
import Commands
data Runnable = forall r . (Exec r,Show r, Read r) => Run r
instance Show Runnable where
show (Run a) = "Run " ++ show a
instance Exec Runnable where
run (Run a) = run a
rate (Run a) = rate a
alias (Run a) = alias a
instance Read Runnable where
readPrec = readRunnable
-- read an existential as any of hidden types ts
class ReadAsAnyOf ts ex where
readAsAnyOf :: ts -> ReadPrec ex
instance ReadAsAnyOf () ex where
readAsAnyOf ~() = mzero
instance (Read t, Show t, Exec t, ReadAsAnyOf ts Runnable) => ReadAsAnyOf (t,ts) Runnable where
readAsAnyOf ~(t,ts) = r t `mplus` readAsAnyOf ts
where r ty = do { m <- readPrec; return (Run (m `asTypeOf` ty)) }
readRunnable :: ReadPrec Runnable
readRunnable = prec 10 $ do
Ident "Run" <- lexP
parens $ readAsAnyOf runnableTypes
-- | Reads the configuration files or quits with an error
readConfig :: FilePath -> IO Runnable
readConfig f =
do s <- readFile f
case reads s of
[(config,_)] -> return config
[] -> error ("Corrupt config file: " ++ f)
_ -> error ("Some problem occured. Aborting...")
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