Add files

src/Loop/Data.hs

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+{-# LANGUAGE StrictData #-}
+{-# LANGUAGE TemplateHaskell #-}
+
+module Loop.Data where
+
+data ConcurrentEffect world
+    = NoConcurrentEffect
+    | ConcurrentEffect
+        { _immediateEffect :: world -> world
+        , _sideEffect :: IO (world -> Maybe world)
+        }