title: Octave: I cannot change the value of a global variable after clearing it
body: <p>I have defined a global variable <code>global x=-2</code>. Once created, global variables cannot be reassigned, i.e., <code>x=7</code> will not change the <code>-2</code> value of <code>x</code>. For this reason I clear the variable. </p>
  
  <pre><code>&gt;&gt; clear x
  </code></pre>
  
  <p>I check that the variable does not exist any more.</p>
  
  <pre><code>&gt;&gt; exist("x")
  ans = 0
  </code></pre>
  
  <p>But when I create the global variable again with a new value, for example, <code>global x=7</code> I get the global variable in the old value.</p>
  
  <pre><code>&gt;&gt; global x=7
  &gt;&gt; x
     x = -2
  </code></pre>
  
  <p>Why is this happening? Is the variable <code>x</code> not really deleted?</p>