Module type Persistent.S

type t
type key
val empty : t

empty an empty index

val string : t -> key -> string

string idx key returns data associated with the provided key. Returns an empty string if there are no data.

val key : t -> string -> key

key idx data returns the key associated with data, if no key is associated then Key.null is returned

val register : t -> string -> t

register idx data registers data in the index idx. If data is already registered, then the index is returned unchanged. Otherwise returns an index where a fresh new key is associated with data.

val registered : t -> string -> bool

registered idx data is true if data was registered in the index.