Add mapIncremental (Monadic, not unsafe)

src/Reflex/Class.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE BangPatterns #-}
+/{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DefaultSignatures #-}
@@ -745,6 +745,10 @@ mergeList es = mergeWithFoldCheap' id es
 unsafeMapIncremental :: (Reflex t, Patch p, Patch p') => (PatchTarget p -> PatchTarget p') -> (p -> p') -> Incremental t p -> Incremental t p'
 unsafeMapIncremental f g a = unsafeBuildIncremental (fmap f $ sample $ currentIncremental a) $ g <$> updatedIncremental a
 
+
+mapIncremental :: (Reflex t, Patch p, Patch p', MonadHold t m) => (PatchTarget p -> PatchTarget p') -> (p -> p') -> Incremental t p -> m (Incremental t p')
+mapIncremental f g a = buildIncremental (fmap f $ sample $ currentIncremental a) $ g <$> updatedIncremental a
+
 -- | Create a new 'Event' combining the map of 'Event's into an 'Event' that
 -- occurs if at least one of them occurs and has a map of values of all 'Event's
 -- occurring at that time.