title: set-car!, set-cdr! unbound in racket?
body: <p>I am just trying to do very simple code with <code>set-car!</code> and <code>set-cdr!</code> in <code>racket</code>, but I got the error: <code>expand: unbound identifier in module in: set-car!</code> and <code>expand: unbound identifier in module in: set-cdr!</code></p>
  
  <p>Aren't they defined in <code>racket</code>? Could anyone help?</p>