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Re: Custom dependencies

From: Kai Großjohann
Subject: Re: Custom dependencies
Date: Tue, 08 Apr 2003 14:56:09 +0200
User-agent: Gnus/5.090018 (Oort Gnus v0.18) Emacs/21.3.50 (gnu/linux)

Dave Love <address@hidden> writes:

> "Stefan Monnier" <monnier+gnu/emacs/address@hidden> writes:
>> - The case as above where variable A has a non-trivial :set function
>>   which depends on variable B, so that when B is changed something
>>   should be done to A.
>>   It seems that the :set-after thingy is a good way to specify the
>>   dependency, but it doesn't describe what should be done to A
>>   when B changes.
> I think it does.  A should be re-set from its current value, since
> something it depends on has changed.  Are there cases in which that
> would be wrong?

So, let's see.  We have (defcustom A ... :set-after '(B) ... :set
...something.long.here...).  And Dave suggests to call the :set
function from A after B has changed.  So whenever a variable X is
changed, we have to look through all other variables Y to see if they
mention X in the :set-after list.

>>   Kai suggests turn A off and back on, but you seem object to it.
> I don't remember that, and it's not anything I thought I was objecting
> to.  It's not a question of off and on in this case anyhow -- the
> state that changes is the contents of a hash table.

My thinking was as follows: (utf-translate-cjk-mode -1) clears the
hash table so that CJK unification is not done.  A subsequent
(utf-translate-cjk-mode 1) statement would then look at
current-language-environment and populate the hash table accordingly.

Of course, it is better to just populate the hash table in the right
way, without clearing it first.

>>   I believe that you object only to
>>   set-language-environment doing it, not to the off&on thing: it
>>   should be done by custom without set-language-environment
>>   (or current-language-environment for that matter) knowing anything
>>   about utf-translate-cjk-mode.
> Yes, if I understand correctly.

So to look through all variables Y to see if their :set-after list
mentions X, and if so, to call the :set function?

That's a good idea.

(It would be nice to be able to do without the (custom-set-variables
...) block that's now used by Customize, because of the conditionals
I mentioned.)
A preposition is not a good thing to end a sentence with.

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