val map : f:( 'a -> 'b ) -> 'a option -> 'b option
val bind : f:( 'a -> 'b option ) -> 'a option -> 'b option
val iter : f:( 'a -> unit ) -> 'a option -> unit
val filter : f:( 'a -> bool ) -> 'a option -> 'a option
val compare : ( 'a -> 'b -> int ) -> 'a option -> 'b option -> int
val equal : ( 'a -> 'b -> bool ) -> 'a option -> 'b option -> bool
val is_none : 'a option -> bool
val is_some : 'a option -> bool
val value : default:'a -> 'a option -> 'a