;;; CODE
            
(defun shift-proportions (integer-seq  shift &key (type 'primes))
  (let ((number-seq))
    (progn 
      (setf number-seq (cond ((equal type 'primes)
                              (primes 30))
                             ((equal type 'fibonacci)
                              (fibonacci 1 20))
                             ((equal type 'decimal)
                              (gen-integer-step 1 200 1))))
      (setf number-seq (append (reverse (neg! number-seq)) number-seq))
      (loop for i in integer-seq
        when (> i 0)
        collect (nth (+ (car (position-item i number-seq)) shift) number-seq)
        else collect (nth (- (car (position-item i number-seq)) shift) number-seq)))))


;;; EXAMPLE => the integer-seq must include only values from ":type"-system

(shift-proportions '(1 2 3 4 5 -3 2 -1 3 -8) 1 :type 'decimal)
=> (2 3 4 5 6 -4 3 -2 4 -9)
(shift-proportions '(1 2 -13 4 5 -3 2 -1 3 -8) 8 :type 'decimal)
=> (9 10 -21 12 13 -11 10 -9 11 -16)


(shift-proportions '(3 5 -17 -11 23) 1 :type 'primes)
=> (5 7 -19 -13 29)
(shift-proportions '(3 5 -17 -11 23) 5 :type 'primes)
=> (17 19 -37 -29 43)


(shift-proportions '(-5 55 -34 233 -89) 1 :type 'fibonacci)
=> (-8 89 -55 377 -144)
(shift-proportions '(-5 55 -34 233 -89) 3 :type 'fibonacci)
=> (-21 233 -144 987 -377)

 

Your code contains some hard-wired boundaries (e.g., 30 for primes). Perhaps you want to make your boundaries dependant on your input in order to avoid that you could exceed them?

 

Best,

Torsten

you are right, but it is okay for my use - if someone wants to make it smarter, it is very welcome - but I have to do some other things :-)