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most-recent-slide
retract-most-recent-slide
re-slide
slide?

3.2 Slide Registration

Returns a slide structure that be supplied re-slide to make a copy of the slide.

Cancels the most recently created slide, and also returns a slide structure that be supplied to re-slide to restore the slide (usually in a later position).

(re-slide slide [pict])  void?
  slide : slide?
  pict : pict? = (blank)
Re-inserts a slide, lt-superimposeing the given additional pict.

(slide? v)  boolean?
  v : any/c
Returns #t if v is a slide produced by most-recent-slide or retract-most-recent-slide.