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| -rw-r--r-- | src/Internal/NoPersist.hs | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/src/Internal/NoPersist.hs b/src/Internal/NoPersist.hs new file mode 100644 index 0000000..a67e649 --- /dev/null +++ b/src/Internal/NoPersist.hs @@ -0,0 +1,23 @@ +-- Module for not persisting XMonad state. To be used with ExtensibleState +-- for data types that cannot be persisted. +module Internal.NoPersist where + +import Data.Default (Default, def) +import Data.Typeable + +import XMonad (ExtensionClass(..)) + +newtype NoPersist a = NoPersist a + deriving (Typeable) + +instance Show (NoPersist a) where + show (NoPersist _) = show () + +instance (Default a) => Read (NoPersist a) where + readsPrec i s = map (\(_, s) -> (NoPersist def, s)) (readsPrec i s :: [((), String)]) + +instance (Default a) => Default (NoPersist a) where + def = NoPersist def + +instance (Default a, Typeable a) => ExtensionClass (NoPersist a) where + initialValue = NoPersist def |