------------

-- | Filter an 'IndexedFold' or 'IndexedGetter', obtaining an 'IndexedFold'.
--
-- >>> [0,0,0,5,5,5]^..traversed.ifiltered (\i a -> i <= a)
-- [0,5,5,5]
--
-- Compose with 'ifiltered' to filter another 'IndexedLens', 'IndexedIso', 'IndexedGetter', 'IndexedFold' (or 'IndexedTraversal') with
-- access to both the value and the index.
--
-- Note: As with 'filtered', this is /not/ a legal 'IndexedTraversal', unless you are very careful not to invalidate the predicate on the target!
ifiltered :: (Indexable i p, Applicative f) => (i -> a -> Bool) -> Optical' p (Indexed i) f a a
ifiltered p f = Indexed $ \i a -> if p i a then indexed f i a else pure a
{-# INLINE ifiltered #-}

-- | Obtain an 'IndexedFold' by taking elements from another
-- 'IndexedFold', 'IndexedLens', 'IndexedGetter' or 'IndexedTraversal' while a pre
ifiltered :: (Indexable i p, Applicative f) => (i -> a -> Bool) -> Optical' p (Indexed i) f a a
ifiltered p f = Indexed $ \i a -> if p i a then indexed f i a else pure a
ifiltered p f = Indexed $ \i a -> if p i a then indexed f i a else pure a