modify proportion-list for "gen-length-constant"

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;;;; A WAY TO MUTATE/MODIFY A PROPORTION-LIST FOR "gen-length-constant"
;;;; the SUM in all generations is CONSTANT

;;;; FUNCTION
(defun modify-prop-seq (generations values &key (value-step 1) (chance 1.0))
  (append (list values)
          (loop repeat (- generations 1)
            with rnd-seq 
            with new-seq
            
            do (if (prob? chance)
                 (setq rnd-seq (rnd-sample-seq 2 values)
                       new-seq (list (+ (car rnd-seq) value-step) (- (car (rest rnd-seq)) value-step))
                       values (loop for i in (pattern-map  (list (append (list rnd-seq) (list new-seq))) values)
                                when (> i 0) 
                                collect i))
                 (append values))
            
            collect values)))

;;;; tests
(modify-prop-seq 5 '(1 2 3 4 5 6 7 8 9))
(modify-prop-seq 5 '(2 1 8 5 1 3) :value-step 1 :chance 0.9)
(modify-prop-seq 5 '(4 4 4 4 4) :value-step 1 :chance 0.5)


;;;; practical-use -> every generation in 1 bar
(loop for i in (modify-prop-seq 5 '(2 1 8 5 1 3) :value-step 1 :chance 0.8)
  collect (gen-length-constant i '4/4))

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