s a     -> (i, a)
-- ('^@?!') :: s -> 'IndexedFold' i s a       -> (i, a)
-- ('^@?!') :: s -> 'IndexedLens'' i s a      -> (i, a)
-- ('^@?!') :: s -> 'IndexedTraversal'' i s a -> (i, a)
-- @
(^@?!) :: s -> IndexedGetting i (Endo (i, a)) s a -> (i, a)
s ^@?! l = ifoldrOf l (\i x _ -> (i,x)) (error "(^@?!): empty Fold") s
{-# INLINE (^@?!) #-}

-- | Retrieve the index of the first value targeted by a 'IndexedFold' or 'IndexedTraversal' which is equal to a given value.
--
-- @
--
(^@?!) :: s -> IndexedGetting i (Endo (i, a)) s a -> (i, a)
s ^@?! l = ifoldrOf l (\i x _ -> (i,x)) (error "(^@?!): empty Fold") s
s ^@?! l = ifoldrOf l (\i x _ -> (i,x)) (error "(^@?!): empty Fold") s