Gumowski-mira写像の点列生成(gnuplotで描画する)

gm.scm

#!/usr/bin/env gosh

(use gauche.generator)
(use gauche.parseopt) 
(use srfi-27) ; 乱数
(use srfi-1)  ; list
(define (make-gm-generator a m x0 y0) 
  (define (f x)
    (let1 xx (* x x)
      (+ (* m x) (/ (* 2 (- 1 m) xx) (+ 1 xx) ) )
      ))
  (define (make-gm-map a m)
    ;;
    (lambda(xn yn fxn)
      (let* [( xn1  (+ yn (* a (- 1 (* 0.05 yn yn) ) yn) fxn ) )
             ( fxn1 (f xn1) )
             ( yn1  (- fxn1 xn))]
        (values xn1 yn1 fxn1)
        )))
  (let1 gm-map (make-gm-map a m)
    (generate
      (lambda (yield)
        (let loop [(xn x0) (yn y0) (fxn (f x0) ) ] 
          (receive (xn1 yn1 fxn1) (gm-map xn yn fxn)
            (yield (cons xn yn) )
            (loop xn1 yn1 fxn1)
            ) ) ) ) ) )

(define (main args)
  (let-args (cdr args)
    [[ ndrop "ndrop=i"]
     [ ntake "ntake=i"]
     [ ntraj "ntraj=i"]
     [ par-a "a=n"]
     [ par-m "m=n"]
     . args
     ]

    (let* [(make-g (lambda() 
                     (gconcatenate
                       (apply gmap
                              ($ list->generator $ list $*)
                              (list-tabulate 
                                ntraj 
                                (lambda (i)
                                  (gtake 
                                    (gmap cons 
                                          (gdrop 
                                            (make-gm-generator 
                                              par-a par-m 
                                              (- (random-real) 0.5 ) 
                                              (- (random-real) 0.5 ) )
                                            ndrop)
                                          (grange) ) ntake ) 
                                  ) ) ) ) ) )]
      (let1 frame 
        (let* [(g (make-g))
               (p0 (g))]
          (generator-fold 
            (lambda (p minmax)
              ;#?= minmax
              ;#?= (cadr minmax)
              `( 
                 ( ,(min (caar minmax) (caar p) ) . ,(min (cdar minmax) (cdar p) ) )
                 .
                 ( ,(max (cadr minmax) (caar p) ) . ,(max (cddr minmax) (cdar p) ) ) ) ) 
            `(,(car p0) . ,(car p0) ) g))

        ;#?= frame
        (format #t "~a ~a 0\n" (caar frame) (cdar frame) )
        (format #t "~a ~a 0\n" (cadr frame) (cddr frame) )
        )
      ;;

      (do-generator (p (make-g) ) 
        (format #t "~a ~a ~a\n" (caar p) (cdar p) (cdr p) )
        ) ) ) )