type t
external (+) : t -> t -> t = "%orint"
val (-) : t -> t -> t
external (&) : t -> t -> t = "%andint" external (*) : t -> t -> t = "%xorint"
val none : tval thread_background_priority_for_indexing : tval thread_background_priority_for_editing : tval thread_background_priority_for_all : t