Module Types.Variance

type t
type f =
| May_pos
| May_neg
| May_weak
| Inj
| Pos
| Neg
| Inv
val null : t
val full : t
val covariant : t
val may_inv : t
val union : t -> t -> t
val inter : t -> t -> t
val subset : t -> t -> bool
val eq : t -> t -> bool
val set : f -> bool -> t -> t
val mem : f -> t -> bool
val conjugate : t -> t
val get_upper : t -> bool * bool
val get_lower : t -> bool * bool * bool * bool