title: Are variable array parameters allowed to have as index variables outside the function?
body: <p>My book states: "The expression used to specify the length of" a variable array "could refer to variables outside the function".
  I guess this is what the book means:</p>
  
  <pre><code>int main(void)
  {
     int xternal = 3;
     int variable_array[xternal];
     function(variable_array);
  }
  
  void function(int variable_array[xternal])
  {
     ...
  }
  </code></pre>
  
  <p>I understood that variables outside the function are invisible to it. Am I wrong?</p>