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diff --git a/src/Data/InOrOut.hs b/src/Data/InOrOut.hs
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+module Data.InOrOut where
+
+
+-- | This wrapper is useful for tagging another type
+--   as being of either an In variety or an Out variety.
+--
+--   For example, incoming messages can be tagged as In
+--   and outgoing messages could be tagged as Out.
+--
+--   Another use case is tagging handles so that
+--   you only output to Out Handle and only input
+--   from In Handle.
+data InOrOut a = In a | Out a