yampa: Make FRP.Yampa.Event.maybeToEvent public. Refs #267.

The function FRP.Yampa.Event.maybeToEvent is labelled as internal, yet
it is being exported by the module. The function is useful and is being
used in the wild, so removing it now would break existing applications.

This commit makes the function "officially" public. It changes the
comment stating that it is internal, and it moves it within the module
to a location that makes more sense in terms of explaining the API.

yampa/src/FRP/Yampa/Event.hs

@@ -35,9 +35,6 @@ module FRP.Yampa.Event
     , noEventFst
     , noEventSnd
 
-      -- * Internal utilities for event construction
-    , maybeToEvent
-
       -- * Utility functions similar to those available for Maybe
     , event
     , fromEvent
@@ -64,6 +61,10 @@ module FRP.Yampa.Event
     , filterE
     , mapFilterE
     , gate
+
+      -- * Utilities for easy event construction
+    , maybeToEvent
+
     )
   where
 
@@ -167,16 +168,6 @@ instance NFData a => NFData (Event a) where
   rnf NoEvent   = ()
   rnf (Event a) = rnf a `seq` ()
 
--- * Internal utilities for event construction
-
--- These utilities are to be considered strictly internal to Yampa for the time
--- being.
-
--- | Convert a maybe value into a event ('Event' is isomorphic to 'Maybe').
-maybeToEvent :: Maybe a -> Event a
-maybeToEvent Nothing  = NoEvent
-maybeToEvent (Just a) = Event a
-
 -- * Utility functions similar to those available for Maybe
 
 -- | An event-based version of the maybe function.
@@ -304,3 +295,10 @@ mapFilterE f e = e >>= (maybeToEvent . f)
 gate :: Event a -> Bool -> Event a
 _ `gate` False = NoEvent
 e `gate` True  = e
+
+-- * Utilities for easy event construction
+
+-- | Convert a maybe value into a event ('Event' is isomorphic to 'Maybe').
+maybeToEvent :: Maybe a -> Event a
+maybeToEvent Nothing  = NoEvent
+maybeToEvent (Just a) = Event a