title: how do I convert this Scheme code to Racket
body: <p>I am new to scheme. This is code sample from SICP course of MIT.</p>
  
  <pre><code> (define (+ x y)
    (if (= x 0)
        y
        (+ (-1+ x) (1+ y))))
  </code></pre>
  
  <p>How do I convert this to Racket code? I want to convert to Racket because I am using DrRacket for running codes and I like that. It worked until now but complained about increment operators of scheme.</p>
  
  <p>The errors I get are:</p>
  
  <ol>
  <li><code>define-values: cannot change constant variable: +</code></li>
  <li><code>reference to undefined identifier: -1+</code></li>
  </ol>