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Re: `append' vs. `nconc'
From: |
Pascal J. Bourguignon |
Subject: |
Re: `append' vs. `nconc' |
Date: |
Thu, 31 Dec 2015 04:45:26 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Emanuel Berg <embe8573@student.uu.se> writes:
> OK, so for example this:
>
> (setq completion-ignored-extensions
> (append completion-ignored-extensions '(".bcf" ".run.xml")) )
>
> Is better as:
>
> (nconc completion-ignored-extensions (list ".bcf" ".run.xml"))
>
> ?
No. You should never use nconc only for effect (just like delete, etc).
Always re-assign the modified list:
(setf completion-ignored-extensions
(nconc completion-ignored-extensions (list ".bcf" ".run.xml")))
otherwise it will break when the place is bound to nil. (nil is a symbol
and cannot be mutated into a cons cell!).
--
__Pascal Bourguignon__ http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk
- Re: Error: Setting the shell in sh-mode via a local variable does not work, (continued)
- Re: Error: Setting the shell in sh-mode via a local variable does not work, Teemu Likonen, 2015/12/30
- `append' vs. `nconc' (was: Re: Error: Setting the shell in sh-mode via a local variable does not work), Emanuel Berg, 2015/12/30
- Re: `append' vs. `nconc', Teemu Likonen, 2015/12/30
- Re: `append' vs. `nconc', Emanuel Berg, 2015/12/30
- Message not available
- Re: `append' vs. `nconc',
Pascal J. Bourguignon <=
- Re: `append' vs. `nconc', Emanuel Berg, 2015/12/30
- Re: `append' vs. `nconc', tomas, 2015/12/31
- Re: `append' vs. `nconc', Emanuel Berg, 2015/12/31
- Message not available
- Re: `append' vs. `nconc', Pascal J. Bourguignon, 2015/12/31
- Re: `append' vs. `nconc', Emanuel Berg, 2015/12/30
- Message not available
- Re: `append' vs. `nconc', Pascal J. Bourguignon, 2015/12/31
- Re: `append' vs. `nconc', Emanuel Berg, 2015/12/31
- Re: `append' vs. `nconc', tomas, 2015/12/31
- side effects, list sharing [was: `append' vs. `nconc'], Drew Adams, 2015/12/31
- Re: side effects, list sharing [was: `append' vs. `nconc'], Emanuel Berg, 2015/12/31