;;;;;;; problem 3.13

(define ((henon-map alpha) x y return failure)
  (if (or (> x 1) (< x -1) (> y 1) (< y -1))
      failure)
  (return (- (* x (cos alpha))
	     (* (- y (square x)) (sin alpha)))
	  (+ (* x (sin alpha))
	     (* (- y (square x)) (cos alpha)))))

(define window (frame -1. 1. -1. 1.))

(explore-map window (henon-map 1.21) 2000)