Compose two optics when the piece of the whole returned by the first optic is needed by the set operator of the second optic.
Compose two optics when the piece of the whole returned by the first optic is needed by the set operator of the second optic. This is more powerful but requires unifying the error types.
Compose two optics when the piece of the whole returned by the get operator of the first optic is not needed by the set operator of the second optic.