# Exercise 2.61

Here is the `adjoin-set`

procedure for the ordered representation using half as many steps as with the unordered representation.

```
(define (adjoin-set x set)
(cond ((null? set) (list x))
((< x (car set)) (cons x set))
((= x (car set)) set)
(else (cons (car set) (adjoin-set x (cdr set))))))
```

Note that we could easily make the procedure tail recursive.