title: Leiningen: How to define constants in project.clj?
body: <p>I have some values repeated in my <code>project.clj</code> like below:</p>
  
  <pre class="lang-lisp prettyprint-override"><code>(defproject foo "0.1.0-SNAPSHOT"
    ...
  
    :dependencies [[bar "3.4.5"]
                   [baz "3.4.5"]
                   [bat "3.4.5"]]
  
    ...)
  </code></pre>
  
  <p>I would like to use some sort of constant here so, when these libraries get updated to <code>3.5.0</code> for example, I have to change just one place.</p>
  
  <p>What is the best practise here? Best I can come up with is this:</p>
  
  <pre class="lang-lisp prettyprint-override"><code>(def deps-version "3.4.5")
  
  (defproject foo "0.1.0-SNAPSHOT"
    ...
  
    :dependencies [[bar ~deps-version]
                   [baz ~deps-version]
                   [bat ~deps-version]]
  
    ...)
  </code></pre>