kwrooijen

(use-modules (srfi srfi-1)
             (rnrs))

(define (transform-at l i val)
  (let-values (((left right) (split-at l i)))
    (append left (cons val (cdr right)))))

(display (transform-at '(1 2 3) 1 5)) ;=> '(1 5 3)

kwrooijen

;; Very clean, but is not tail recursive!
(define (dec->bin n)
  (cond ((zero? n) '())
        (else (cons (remainder n 2)
                    (dec->bin (quotient n 2))))))

;; Not so clean, but is tail recursive.
(define (dec->bin n)
  (letrec ((recc (lambda (acc n)
                   (cond ((zero? n) acc)