#lang scheme
(require racket/trace)
(define (comp fact should)
  (println fact)
  (println should)
  (display "\n"))

;iterative
(define (evenpowlistit n m)
  (define (loop i result)
        (if (= i 0)
            result
            (loop (- i 2) (cons (expt m i) result))))
  (if (not (and (> n 0) (integer? n))) '()
      (loop (+ n n) '())))

(comp (evenpowlistit -1 2) '())
(comp (evenpowlistit 1.3 2) '())

(comp (evenpowlistit 3 2) '(4 16 64))
(comp (evenpowlistit 5 1) '(1 1 1 1 1))
(comp (evenpowlistit 1 2) '(4))

;recursive
  (define (rec n m cap)
    (if (> n cap) '()
        (cons  (expt m n) (rec (+ n 2) m cap))))
(define (evenpowlistrec n m)
  (if (not (and (> n 0) (integer? n))) '()
      (rec 2 m (+ n n))))

(comp (evenpowlistrec -1 2) '())
(comp (evenpowlistrec 1.3 2) '())

(comp (evenpowlistrec 3 2) '(4 16 64))
(comp (evenpowlistrec 5 1) '(1 1 1 1 1))
(comp (evenpowlistrec 1 2) '(4))



(trace evenpowlistit)
(evenpowlistit 4 3)

(trace rec)
(evenpowlistrec 4 3)