Keys
The type for key information.
create i is a new key with information i.
info k is k's information.
Existential keys
Exisential keys allow to compare keys. This can be useful for functions like filter.
The type for existential keys.
val hide_type : 'a key -> thide_type k is an existential key for k.
val equal : t -> t -> boolequal k k' is true iff k and k' are the same key.
val compare : t -> t -> intcompare k k' is a total order on keys compatible with equal.