(define generate-sequence-processor
  (lambda (f g base-value next)
    (lambda (low high)
      (if (> low high)
          base-value
          (g (f low)
             ((generate-sequence-processor f g base-value next) (next low)
                                                                high))))))

(define harm
  (lambda (n)
    ((generate-sequence-processor (lambda (i) (/ 1 i))
                                  +
                                  0
                                  (lambda (i) (+ i 1))) 1 n)))

(define sum-from-to
  (generate-sequence-processor (lambda (i) i)
                               +
                               0
                               (lambda (i) (+ i 1))))

(define sum-odd-integers-from-to
  (generate-sequence-processor (lambda (i) (if (odd? i) i (+ 1 i)))
                               +
                               0
                               (lambda (i) (+ i 2))))

(define sum-even-integers-from-to
  (generate-sequence-processor (lambda (i) (if (even? i) i (+ 1 i)))
                               +
                               0
                               (lambda (i) (+ i 2))))

(define factorial
  (lambda (n)
    ((generate-sequence-processor (lambda (i) i)
                                  *
                                  1
                                  (lambda (i) (+ i 1))) 1 n)))

(define double-factorial
  (lambda (n)
    ((generate-sequence-processor (lambda (i) i)
                                  *
                                  1
                                  (lambda (i) (+ i 2))) 
                                    (if (even? n) 2 1) n)))