title: Cannot find a solution to K&R exercise 4-6
body: <p>In K&amp;R we have managed to create an RPN.</p>
  
  <p>The exercise now is to:</p>
  
  <blockquote>
    <p>Add commands for handling variables, (It's easy to provide twenty-six
    variables with single letter names.) Add a variable for the most
    recently printed value.</p>
  </blockquote>
  
  <p>So this is meant to act somewhat like the Python interpreter, where we can do:</p>
  
  <pre><code>&gt;&gt;&gt;5
  &gt;&gt;&gt;_ (where _ prints 5)
  &gt;&gt;&gt;_ + 5 (which prints 10)
  </code></pre>
  
  <p>or
  A = 5
  _ + A (which prints 10)</p>
  
  <p>and so on, but I'm not so sure about how I want to go about it in C. I just feel stumped.</p>