Introduction

nitomic is Datomic's peer API (datomic.api) ported to clonim, a Clojure compiler that targets Nim. Datomic programs written against datomic.api compile to native binaries, with no JVM involved.

(require '[datomic.api :as d])

(d/create-database "datomic:mem://hello")
(def conn (d/connect "datomic:mem://hello"))

@(d/transact conn [{:db/ident :person/name
                    :db/valueType :db.type/string
                    :db/cardinality :db.cardinality/one}])
@(d/transact conn [{:person/name "Ada"} {:person/name "Grace"}])

(d/q '[:find [?n ...] :where [_ :person/name ?n]] (d/db conn))
;=> ["Ada" "Grace"]

A clean-room port, checked against the real thing

Datomic Pro 1.0.7705 ships its peer library as AOT-compiled JVM classes, with no Clojure source. nitomic is therefore a clean-room reimplementation of the peer API in Clojure that clonim can compile.

It is checked against Datomic itself. The same test programs run on the JVM against Datomic Pro and natively against nitomic, and their outputs must match line for line. The main one of those programs is Datomic's own getting-started walkthrough, which is what the Getting started part of this book explains step by step.

The bootstrap database is also taken from Datomic. The system partitions, value types and attributes, with Datomic's own entity ids, docs and transaction ids, were dumped from a fresh datomic:mem database. New entity ids are allocated the way Datomic allocates them:

• transaction ids are t in partition 3;
• other ids share the t counter in their partition;
• attributes get their own counter in the db partition.

So the ids a program sees are the ids Datomic would give it.

How to read this book

• Installation and Your first program get a program compiled and running.
• Getting started walks through the Seattle example in examples/seattle/, explaining each step and showing the output it produces.
• The Reference part lists what is supported, where nitomic differs from Datomic, and how the port is tested.