presentation-type OPTIONS

• To: jclose@ads.com, clim@BBN.COM
• Subject: presentation-type OPTIONS
• From: Scott McKay <SWM@stony-brook.scrc.symbolics.com>
• Date: Thu, 22 Oct 1992 12:46-0400
• In-Reply-To: <9210212056.AA00538@thames.ads.com>

    Date: Wed, 21 Oct 1992 16:56 EDT
    From: Jeff Close <jclose@chesapeake.ads.com>


    A couple of quickie about pres-type options:  when specifying
    additional options in the definition of a presentation type,
    a) do these options inherit naturally or must they be explicitly
    specified in other pres-type definitions based on this one, and 

Presentation type options do not inherit.  This was an explicit design
decision, but since it was made about three years ago, I can no longer
remember what the rationale was.

    b) is it proper (i.e. does it work) to specify defaults for these
    options like keywords, or do such specifications have no effect?

Specifying a default works.  For example,

  (define-presentation-type pathname ()
    :inherit-from t                     ;enforce CL definition
    :history t
    :options ((default-type nil)
              (default-version :newest)
              (merge-default t)))

and

  (define-presentation-type integer (&optional low high) 
    :options ((base 10 nil (integer 2 36))
              (radix nil nil boolean (:prompt "Display the base")))
    :history number
    :inherit-from `((rational ,low ,high)
                    :base ,base :radix ,radix))


0,,

• Re: presentation-type OPTIONS
• From: Jeff Close <jclose@chesapeake.ads.com>

• presentation-type OPTIONS
• From: Jeff Close <jclose@chesapeake.ads.com>

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