title: Check if character is in string
body: <p>In Common Lisp, is there a predicate to test whether a given character is part of a string? Or more generally, if an element is a member of a vector?</p>
  
  <p>Something like:</p>
  
  <pre><code>(char-in #\o "foo")
  </code></pre>
  
  <p>I was able to implement it as</p>
  
  <pre><code>(defun char-in (c s)
    (member c (coerce s 'list)))
  </code></pre>
  
  <p>Is there a better way?</p>