(define c&c
  (lambda (expression s slst errvalue)
    (if (null? slst)
        errvalue
        (if (list? (car slst))
            (if (eq? errvalue
                     (c&c (cons 'car (list expression)) s (car slst) errvalue))
                (if (null? (cdr slst))
                    errvalue
                    (c&c (cons 'cdr (list expression)) s (cdr slst) errvalue))
                (c&c (cons 'car (list expression)) s (car slst) errvalue))
            (if (eq? s (car slst))
                (cons 'car (list expression))
                (c&c (cons 'cdr (list expression)) s (cdr slst) errvalue))))))
;Value: c&c

(define car&cdr
  (lambda (s slst errvalue)
    (if (eq? errvalue (c&c 'lst s slst errvalue))
        errvalue
        (list 'lambda '(lst) (c&c 'lst s slst errvalue)))))
;Value: car&cdr

(car&cdr 'a '(a b c) 'fail)
;Value 48: (lambda (lst) (car lst))

(car&cdr 'c '(a b c) 'fail)
;Value 49: (lambda (lst) (car (cdr (cdr lst))))

(car&cdr 'dog '(cat lion (fish dog) pig) 'fail)
;Value 50: (lambda (lst) (car (cdr (car (cdr (cdr lst))))))

(car&cdr 'dog '(cat lion (fish goose) (fish dog) pig) 'fail)
;Value 51: (lambda (lst) (car (cdr (car (cdr (cdr (cdr lst)))))))

(car&cdr 'doge '(cat lion (fish goose) (fish dog) pig) 'fail)
;Value: fail

(car&cdr 'a '(b c) 'fail)
;Value: fail