Made Signal a newtype, so it's easier to pass around (#4)

Author: robertdp

src/Wire/Signal.purs

@@ -6,27 +6,44 @@ import Effect.Ref as Ref
 import Wire.Event (Event)
 import Wire.Event as Event
 
-type Signal a
-  = { event :: Event a
-    , modify :: (a -> a) -> Effect Unit
-    , read :: Effect a
-    , write :: a -> Effect Unit
-    , cancel :: Effect Unit
-    }
-
-create :: forall a. a -> Effect (Signal a)
+newtype Signal a
+  = Signal
+  { event :: Event a
+  , modify :: (a -> a) -> Effect Unit
+  , read :: Effect a
+  , write :: a -> Effect Unit
+  }
+
+create :: forall a. a -> Effect { signal :: Signal a, cancel :: Effect Unit }
 create init = do
   value <- Ref.new init
   inner <- Event.create
   let
-    read = Ref.read value
+    read' = Ref.read value
 
-    write a = modify (const a)
+    write' a = modify' (const a)
 
-    modify f = Ref.modify f value >>= inner.push
+    modify' f = Ref.modify f value >>= inner.push
 
-    event =
+    event' =
       Event.makeEvent \emit -> do
         Ref.read value >>= emit
         Event.subscribe inner.event emit
-  pure { event, read, write, modify, cancel: inner.cancel }
+
+    signal = Signal { event: event', read: read', write: write', modify: modify' }
+  pure { signal, cancel: inner.cancel }
+
+event :: forall a. Signal a -> Event a
+event (Signal s) = s.event
+
+read :: forall a. Signal a -> Effect a
+read (Signal s) = s.read
+
+write :: forall a. a -> Signal a -> Effect Unit
+write a (Signal s) = s.write a
+
+modify :: forall a. (a -> a) -> Signal a -> Effect Unit
+modify f (Signal s) = s.modify f
+
+distinct :: forall a. Eq a => Signal a -> Signal a
+distinct (Signal s) = Signal s { event = Event.distinct s.event }