The following line in my code is giving me an unbound identifier error.

```
((symbol<? x (car l)) #f)

```

can anybody please explain to me why i am getting this error and how I could resolve it.

Here's the whole code:

```
; tests membership in ordered list of symbols

(define (member? x l)
 (cond

   ((null? l) #f)
   ((symbol=? x (car l)) #t)
   ((symbol<? x (car l)) #f)
   (else (member? x (cdr l)))))

```