title: Scheme - sum of list
body: <p>I'm trying to implement a function which calc sum of list  , its name is <code>sum</code> - </p>
  
  <pre><code>(define (sum elemList)
    (if
     (null? elemList)
     (+ (car elemList) (sum (cdr elemList)))
     0
    )
   )
  </code></pre>
  
  <p>The above implementation gives wrong result  , for example  - </p>
  
  <pre><code>&gt; (sum (list 1 2 3 4 ))
  0
  </code></pre>
  
  <p>What I did wrong here ? </p>