title: Scheme Global variable won't change
body: <p>I'm pretty new to Scheme and I'm currently working in DR Racket to learn it. So basically my problem is that I'm having trouble permanently changing  global variable.</p>
  
  <p>This is my change function:</p>
  
  <pre><code>(define (change b)
    (set! b (- b 1)) b)
  </code></pre>
  
  <p>As you can note I return the value of a at the end of the function.
  And this is the output on the console.</p>
  
  <pre><code>&gt; (define a 4)
  &gt; (change a)
  3
  &gt; a
  4
  </code></pre>
  
  <p>As you can see, in the function it returned the value of 3 (4 - 1). But it seems as though the global variable didn't actually change when i call it after the function. How do I leave it changed? Thanks in advance.</p>