From: Eric Abrahamsen <eric@ericabrahamsen.net>
To: help-gnu-emacs@gnu.org
Subject: Two questions about generalized variables
Date: Sun, 21 Feb 2016 13:16:43 +0800 [thread overview]
Message-ID: <87ziuu4p8k.fsf@ericabrahamsen.net> (raw)
I'm starting to learn a bit more about generalized variables, the gv-*
stuff and macroexpand-*, what have you, and I have two
practical/learning questions I hope someone can help me with.
The first is working with plists. It can be a pain setting many plist
entries at once, particularly when there's lots of surrounding
conditional code. You either have to keep doing
"(setq plist-var (plist-put plist-var ..."
Or else use a backquote template, but that's not always practical.
It looks like plist-get doesn't return a setf-able place. I was thinking
of making a "with-plist-slots" macro, and looking at the `with-slots'
macro as inspiration, but `with-slots' also requires setf-able places.
Is there a way to define something to make that work?
The second question is setting hashtable entries. Right now I have code
like this:
(setf (gethash uuid my-hashtable)
(append (list (list 'thingone 'thingtwo))
(gethash uuid my-hashtable)))
I assume this is no more or less efficient than let-ting the gethash,
manipulating the value, then using puthash to put it back in. Now I've
written this:
(macroexp-let2 nil entry (gethash uuid my-hashtable)
(setf entry (append (list (list 'thingone 'thingtwo))
entry)))
This is a simplistic example, but -- is this actually going to be any
faster or more efficient than the first version? Does it only access the
hashtable once? Have I just been blinded by the shiny?
Any insights very welcome!
Thanks,
Eric
next reply other threads:[~2016-02-21 5:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-21 5:16 Eric Abrahamsen [this message]
2016-02-21 8:08 ` Two questions about generalized variables Eric Abrahamsen
2016-02-21 13:34 ` Michael Heerdegen
2016-02-21 15:01 ` Eric Abrahamsen
2016-02-21 18:08 ` Michael Heerdegen
2016-02-23 3:19 ` Eric Abrahamsen
2016-02-23 13:28 ` Michael Heerdegen
2016-02-24 2:03 ` Eric Abrahamsen
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