A function to transform a list into a list of cons.

part-cons.rkt

;; Example: 
;; (part-cons '(1 2 3 4 5)) ;; => '((1 . 2) (3 . 4) (5))

(define (part-cons l [acc '()])
  (if (equal? l null)
      acc
      (let ([k (car l)]
            [v (if (null? (cdr l)) null (cadr l))]
            [ll (if (> (length l) 1)
                    (drop l 2)
                    (drop l 1))])
        (if (equal? acc null)
            (part ll (list (cons k v)))
            (part ll (append acc
                             (list (cons k v))))))))