Type safety with type classes (Work in Progress)

Points in time

The AsPointT type class is used when API methods require a point time. With the Datomic API, time is transaction time as recorded by the transactor. Points in time can be specified in absolute time as instances of java.util.Date, or as logical time as a basis T value (of type Long), or as an entity id for a transaction entity (of type Long).

This type class is used by Database.asOf, Database.since, Database.entidAt, and Log.txRange. For example:

val db: Database = …
val db1 = db.asOf(1001)
val db2 = db.since(new java.util.Date)

Permanent entity ids

The AsPermanentEntityId type class is used when API methods require an identifier for an entity that should be already present in the database. In Datomic, entities are identified by their :db/id values of type Long, however, entities can also be identified by lookup refs.

This type class is used by Database.entity, Database.entid, Database.ident, Entity.retract, Fact.retract, SchemaFact.retract, and various excision methods.

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