Overview

Datomic Pro ships a getting-started tutorial built around a small data set about Seattle's neighborhood communities: blogs, mailing lists, Twitter feeds, chambers of commerce and so on. The tutorial lives in the Datomic distribution as samples/seattle/getting-started.clj, a file of forms meant to be evaluated one at a time in a REPL.

nitomic carries that tutorial as a single program:

examples/seattle/
├── getting_started.clj   # the walkthrough, as one program
├── seattle-schema.edn    # the schema: 10 attributes and their enums
├── seattle-data0.edn     # the initial data: 150 communities
└── seattle-data1.edn     # more data, added later: 108 more communities

The data files come from the Datomic Pro distribution, which is licensed under the Apache License 2.0.

Running it

From the root of a nitomic checkout:

nimble example
# or, equivalently
clonim run examples/seattle/getting_started.clj --source-path src

The program reads the .edn files by relative path, so run it from the repository root.

Why it prints the way it does

The program runs unchanged on the JVM against Datomic Pro and natively against nitomic, and the two outputs are compared line by line (see How it is tested). Query results are sets, whose iteration order differs between the two implementations, and instants differ from run to run. So instead of printing results directly, the program prints them through two small helpers that produce a canonical form:

(defn- canon-str [x]
  (cond
    (map? x) (str "{" (str/join ", " (sort (map (fn [[k v]] (str (canon-str k) " " (canon-str v))) x))) "}")
    (set? x) (str "#{" (str/join " " (sort (map canon-str x))) "}")
    (vector? x) (str "[" (str/join " " (map canon-str x)) "]")
    (seq? x) (str "(" (str/join " " (map canon-str x)) ")")
    (inst? x) "#inst"
    :else (pr-str x)))

(defn show
  "Print a labelled result; an unordered collection of results is sorted."
  [label x]
  (println (str label ":") (canon-str x)))

(defn show-sorted [label xs]
  (println (str label ":") (str "(" (str/join " " (sort (map canon-str xs))) ")")))

• show prints a label and a value. Map keys and set members are sorted, and every instant prints as #inst.
• show-sorted prints a collection of results as a sorted list.

Every output line quoted in the following chapters is taken from test/expected/getting_started.out, which was recorded on the JVM against Datomic Pro 1.0.7705. nitomic must reproduce it exactly.

The chapters