examples/ex-53.rkt
#lang racket
(require (planet wcy/mpost-wrapper))
(provide main)
(define (main)
  (let* ((u '1cm)
         (A  (point (op*  0.2 u) (op*  0.05 u)))
         (AA (point (op*  0.2 u) (op* -0.05 u)))
         (B  (point (op*  1.0 u) (op*  0.05 u)))
         (BB (point (op*  1.0 u) (op* -0.05 u)))
         (C  (point (op* -0.2 u) (op*  0    0)))
         (D  (point (op* -1.0 u) (op*  0    0)))
         (p (path B  (dir-spec 'up) ".."
                  D  (dir-spec 'down) ".."
                  BB (dir-spec 'up) "--"
                  AA (dir-spec 'down) ".."
                  C  (dir-spec 'up) ".."
                  A  (dir-spec 'down) "--"
                  'cycle)))
    (fill p #:withcolor (op* 0.8 'white))
    (draw p #:withpen (scale '1bp 'pencircle))
    ))