A problem

In Scheme we can use “distinguished values” to handle exceptional cases
- (define (find pred x) (cond ((null? x) #f) ((pred (car x)) (car x)) (else (find pred (cdr x)))))
- (find is-positive? ‘(-3 3 5)) => 3
- (find is-positive> ‘(-3 -5)) => #f

In Scheme we can use “distinguished values” to handle exceptional cases