(** Preservation of [free] operations *)

Theorem free_parallel_inject:
forall f m1 m2 b lo hi m1' b' delta,
inject f m1 m2 ->
free m1 b lo hi = Some m1' ->
f b = Some(b', delta) ->
exists m2',
free m2 b' (lo + delta) (hi + delta) = Some m2'
/\ inject f m1' m2'.