DrRacket - why is this number negative?

问题

So I can not figure out why my numbers are negative in this function. Also, the input for calculate is supposed to be a list of the same 3 if someone could give me a hand with that as well, it would be much appreciated. Thank you.

calculate takes the first number in the list, then multiplies it by the second number in the list and subtracts the third number from the input list.

((calculate '(8 3 7)) '(4 8 2 9)) should return '(29 41 23 44)

(define (calculateHelper n m o L)
  (if (null? L) empty
      (cons ((calculate n m o) (car L)) 
            (calculateHelper n m o (cdr L)))))

;((calculate 8 3 7) '(4 8 2 9))
(define (calculate n m o)
   (lambda (L)
     (if (list? L) (calculate n m o L)
         (- o (* m (+ n L))))))

回答1:

Among other things, your subtraction was inverted. This should help:

(define (calculate n m o)
  (lambda (L)
    (map (lambda (e)
           (- (* m (+ n e)) o))
         L)))

then

> ((calculate 8 3 7) '(4 8 2 9))
'(29 41 23 44)

---

EDIT: to call calculate with a list, you could for example use apply to destructure:

(define (calculate nums)
  (apply (lambda (n m o) 
           (lambda (L)
             (map (lambda (e)
                    (- (* m (+ n e)) o))
                  L)))
         nums))

then

> ((calculate '(8 3 7)) '(4 8 2 9))
'(29 41 23 44)

来源：https://stackoverflow.com/questions/49740700/drracket-why-is-this-number-negative