list->string   scheme

(define (list->string charlist)
  (let* ((len (length charlist))
         (newstr (make-string len))
         (fill-string!
          (lambda (str i len charlist)
            (if (= i len)
                str
                (begin (string-set! str i (car charlist))
                       (fill-string! str (+ i 1) len (cdr charlist)))))))
    (fill-string! newstr 0 len charlist)))