title: Swift make method parameter mutable?
body: <p>How can I deal with this error without creating additional variable? </p>
  
  <pre><code>func reduceToZero(x:Int) -&gt; Int {
      while (x != 0) {
          x = x-1            // ERROR: cannot assign to 'let' value 'x'
      }
      return x
  }
  </code></pre>
  
  <p>I don't want to create additional variable just to store the value of x. Is it even possible to do what I want?</p>