title: Create unary operator in R
body: <p>Is it possible to create a unary operator in R? I know it's possible to create binary operator like this:</p>
  
  <pre><code>setGeneric("%power%", function(x, y) x ^ y)
  2 %power% 4
  </code></pre>
  
  <p>But is it possible to create a unary operator like <code>-</code>. I tried something like:</p>
  
  <pre><code>setGeneric("%-%", function(x) -x)
  %-% 3
  </code></pre>
  
  <p>But it doesn't work</p>