ProtoLensApplicative.hs

-- pseudo-code, let's consider these types have corresponding lensens
-- from package proto-lens https://github.com/google/proto-lens
data Foo = Foo {foo :: Maybe Bar}

data Bar = Bar {bar :: Maybe Buz}

data Buz
  = Buz
      { buz :: Bool,
        buf :: Int,
        bif :: Integer
      }

-- I'm using bind here to handle Maybe
-- And compose Just values into tuple
-- Is there better/shorter way to do it
-- with some lens-specific functions?
-- Something applicative-like style for lens?
accessBuzBufBif :: Foo -> Maybe (Bool, Int, Integer)
accessBuzBufBif x = do
  buz' <- x ^? mbar . buz
  buf' <- x ^? mbar . buf
  bif' <- x ^? mbar . bif
  return (buz', buf', bif')
  where
    mbar = maybe'foo . _Just . maybe'bar . _Just