Using io-choice.

GHCChoice.hs

@@ -0,0 +1,25 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module GHCChoice where
+
+import Control.Exception
+import CoreMonad
+import Exception
+import GHC
+
+----------------------------------------------------------------
+
+(||>) :: Ghc a -> Ghc a -> Ghc a
+x ||> y = x `gcatch` (\(_ :: IOException) -> y)
+
+----------------------------------------------------------------
+
+{-| Go to the next 'Ghc' monad by throwing 'AltGhcgoNext'.
+-}
+goNext :: Ghc a
+goNext = liftIO . throwIO $ userError "goNext"
+
+{-| Run any one 'Ghc' monad.
+-}
+runAnyOne :: [Ghc a] -> Ghc a
+runAnyOne = foldr (||>) goNext