nreverse (a standard function in Common Lisp) works like reverse, but destructively modifies its input list by turning the pointers around.

> (define lst '(a b c))
lst

> (define back (nreverse lst))
back

> back
(c b a)

> lst
(a)

(define (nreverse x)
  (let ((last '()) (tmp '()))
    (while (pair? x)
      (set! tmp (cdr x))
      (set-cdr! x last)
      (set! last x)
      (set! x tmp))
    last))

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