Why can I not access my Leiningen dependencies with Clojure code?

Question

In Clojure, if I want to pull in the clojure.inspector functions, I can go like this:

(use `[clojure.math.numeric-tower :include (expt)])

From the REPL, and I can now evaluate the function expt.

However, it seems to me that there should be (and probably is) another way to do it - pulling in the code using Leiningen dependencies.

I add this line to my project.clj:

[org.clojure/math.numeric-tower "0.0.2"]

And I restart the REPL to pull in the new dependency. I even do "lein deps" to be safe (there is no output for that command). When I try to evaluate expt, it gives me a RuntimeException, and says its Unable to resolve the symbol.

How can I access the expt function, only using Leiningen dependencies?

Answer 1

You can't. It doesn't work like that. Adding a dependency puts the code on your classpath, which merely means it is available for you to use. In order to actually use the things inside the namespaces, you need to use

(require '[the-namespace :refer [the things you want to use]])

or

(require '[the-namespace :as tn])
(tn/somevar)

or do either of those things in an ns declaration (when not in the REPL and working with a file)

(ns foo
  (:require [the-namespace :as tn]))