title: Ridiculously simple logic still gives error
body: <p>I have two chars.
  Each of them stores digits between 0  and 9.
  I want to find the sum of these two and then modulo 10 to ensure the result in a single digit (0-9)
  And finally convert the result back to char. </p>
  
  <p>I did this but it won't work:</p>
  
  <pre><code>char a = '4';
  char b = '8';
  char c = (char)((a - '0') + (b - '0') % 10);
  </code></pre>