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Re: plist-put modification by side effect


From: Thien-Thi Nguyen
Subject: Re: plist-put modification by side effect
Date: Sun, 01 Feb 2009 00:02:42 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux)

() Dan Davison <davison@stats.ox.ac.uk>
() Sat, 31 Jan 2009 16:06:30 -0500

   I don't get this. It says the plist is altered by side
   effects. So what's with the "but just to be extra careful
   use (setq ...)"  advice?

If PROP is in PLIST, the natural side-effecting operation is
to splice in the VALUE at the position of the old value.  Ok,
fine.  Now, what if PROP is not in PLIST?  How might you
implement that?  How might you implement that, differently?
How might your design decision surprise the unwary caller?

thi




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