title: How does for(i=0; i<5; x=(i++,a++)) work
body: <p>I can't understand how this works and why it produces 
  the following output.</p>
  
  <pre><code>int main()
  {
      int i=0;
      int a=5;
      int x=0;
  
      for(i=0; i&lt;5; x=(i++,a++))
      {
          printf("i=%d a=%d x=%d\n",i,a,x);
      }
  }
  </code></pre>
  
  <p>this give as output:</p>
  
  <pre><code>i=0 a=5 x=0
  i=1 a=6 x=5
  i=2 a=7 x=6
  i=3 a=8 x=7
  i=4 a=9 x=8
  </code></pre>