(define (inc a) (+ a 1))
(define (dec a) (- a 1))

(define (add-recursive a b)
  (if (= a 0) b
      (inc (add-recursive (dec a) b))))

; (add-recursive 4 5)
; (inc (add-recursive 3 5))
; (inc (inc (add-recursive 2 5)))
; (inc (inc (inc (add-recursive 1 5))))
; (inc (inc (inc (inc (add-recursive 0 5)))))
; (inc (inc (inc (inc 5))))
; (inc (inc (inc 6)))
; (inc (inc 7))
; (inc 8)
; 9


(define (add-iterative a b)
  (if (= a 0) b
      (add-iterative (dec a) (inc b))))

; (add-iterative 4 5)
; (add-iterative 3 6)
; (add-iterative 2 7)
; (add-iterative 1 8)
; (add-iterative 0 9)
; 0