The Publics Good

tl;dr ns-publics gives you a list of the the public vars in a Clojure namespace.

When I was writing up my quick note on mapv, I wanted to flesh it out by looking for similar functions in clojure.core. I’ve never really needed to introspect a Clojure namespace like that before, so I started with a web search. That turned up the ns-publics function, which, as it says on the tin, returns all the public vars in the given namespace. Specifically, it returns a map whose keys are symbols, and whose values are the interned vars.1

user=> (in-ns 'foo)
#object[clojure.lang.Namespace 0x66b72664 "foo"]
foo=> (clojure.core/ns-publics 'foo)
foo=> (def bar "BAR!")
foo=> (def ^:private baz "BAZ!")
foo=> (clojure.core/ns-publics 'foo)
{bar #'foo/bar}

Groovy. So for my use case (finding mapv and its relatives) all I have to do is this:

(->> (ns-publics 'clojure.core)
     (filter #(clojure.string/ends-with? % "v")))
(filterv reduce-kv mapv)

Since reduce-kv is something else entirely, it looks like mapv and filterv are the vector-producing siblings. (As reported in that earlier post. 😀)

And speaking of related functions, ns-publics has its share of kin:

It’s nifty, though not surprising, that Clojure has mechanisms for getting at this information. It’s always fun to get a chance to explore another corner of the language.

Questions? Comments? Contact me!

  1. If I take the Clojure guide on vars at face value, interning is the word for the “find-or-create process” that happens when you call def or defn. Return

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