title: emacs/elisp: What is the hash (pound, number sign, octothorp) symbol used for?
body: <p>What does this do? </p>
  
  <pre><code>(add-hook 'compilation-mode-hook #'my-setup-compile-mode)
  </code></pre>
  
  <p>...and is it different than</p>
  
  <pre><code>(add-hook 'compilation-mode-hook 'my-setup-compile-mode)
  </code></pre>