; how-many : list => number
(define (how-many L)
  (cond [(empty? L) 0]
        [(cons? L) 
;         L         ; non-empty list
;         (first L) ; something
;         (rest L)  ; list
;         (how-many (rest L)) ; number
         (+ 1 (how-many (rest L)))
         ]
        ))
"Examples of how-many:"
(how-many empty) "should be" 0
(how-many (cons "Steve" empty)) "should be" 1
(how-many (cons "Deborah" (cons "Steve" empty))) "should be" 2
(how-many (cons "a" (cons "b" (cons "c" (cons (make-posn 3 4) (cons (cons "x" (cons "y" empty)) (cons "d" empty))))))) "should be" 6
(add-up empty) "should be" 0
(add-up(cons 5 empty)) "should be" 5
(add-up(cons 3 (cons -4 (cons 12 empty)))) "should be" 11