goblins-deliberate/deliberate/borda.scm

(define-module (deliberate borda)
  #:export (borda-score))

(define (const-list length value)
  (if (= length 0)
      '()
      (cons value (const-list (- length 1) value))))

(define (borda-score alternatives ranked)
  ;; Check whether all alternatives have been scored
  (if (nil? alternatives)
      '()
      ;; Check whether all ranked alternatives have been scored
      (if (nil? ranked)
	  (let* ((n (length alternatives))
		 (score (/ (- n 1) 2)))
	    ;; Assign average remaining score to all unranked alternatives
	    (map cons alternatives (const-list n score)))
	  ;; Just use next rank
	  (let* ((alt (car ranked))
		(remaining (delete alt alternatives)))
	    (cons (cons alt (length remaining))
		  (borda-score remaining (cdr ranked))))
	  )))