(define-component fence_post ((number x 0mm) (number height 22mm))
  (translate x 0 0
    (union
      (cylinder 2mm height)
      (translate 0 0 height
        (cone 3mm 0mm 5mm)))))

(model
  (params
    (number posts 6 :label "Fence posts" :min 3 :max 9 :step 1))

  (part fence
    (let* ((post_row
             (repeat-union i posts
               (fence_post :x (* i 9mm))))
           (rail_length (+ (* (- posts 1) 9mm) 4mm))
           (rail_center (/ (* (- posts 1) 9mm) 2))
           (bottom_rail
             (translate rail_center 0 8mm
               (box rail_length 2mm 3mm)))
           (top_rail
             (translate rail_center 0 16mm
               (box rail_length 2mm 3mm))))
      (union post_row bottom_rail top_rail)))

  (part carrot
    (translate 20mm -12mm 0
      (loft 18mm
        (circle 1mm)
        (regular-polygon 6 5mm)))))