Mandelbrot fractal in Scheme

mandelbrot.ss

(define (p i c x)
  (cond ((< i 1) "*")
        ((> (magnitude x) 2) " ")
        (else (p (- i 1) c (+ (* x x) c)))))

(do ((y -1 (+ y .05))) ((> y 1))
  (do ((x -2 (+ x .025))) ((> x 1))
    (let ((c (make-rectangular x y)))
      (display (p 99 c c))))
  (newline))