to big nest level of recursion

["Anton V. Belyaev" <anton.belyaev@gmail.com>]

Hi! I wrote a simple function which fails on lists long enougth with
reason "(error "Lisp nesting exceeds `max-lisp-eval-depth'")". But the
function contains right recursion. Does Emacs LISP interpreter unwind
right recursion calls?

(defun contains (lst el)
  (if (null lst)
      nil
    (if (eq (car lst) el)
	t
      (contains (cdr lst) el)
      )
    )
  )

PS: Does Emacs built-in functions have an equivalent of my contains?