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bug#36418: 26.2.90; mapconcat "SEPARATOR must be a string." is incorrect
From: |
Stefan Kangas |
Subject: |
bug#36418: 26.2.90; mapconcat "SEPARATOR must be a string." is incorrect |
Date: |
Sat, 6 Jul 2019 06:17:08 +0200 |
Xu Chunyang <mail@xuchunyang.me> writes:
> C-h f mapconcat says
>
>> SEPARATOR must be a string.
>
> but nil works fine
>
> (mapconcat #'identity '("a" "b") nil)
> ;; => "ab"
This seems to have been added in commit aecbbd57, which fixes
Bug#35710:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=35710
Perhaps Eli would want to weigh in on this?
> and `string-join` relies on this fact (by the way, string-join's
> docstring doesn't explain the case when separator is omitted or nil)
>
> (defsubst string-join (strings &optional separator)
> "Join all STRINGS using SEPARATOR."
> (mapconcat 'identity strings separator))
This could be expanded, in my opinion.
> C-h S mapconcat says
>
>> SEPARATOR, which also must be a string, or a vector or list of
>> characters.
>
> C-h f concat says
>
>> Each argument may be a string or a list or vector of characters (integers).
In other words, since SEPARATOR can be a "list of characters", it
follows that it can also be nil (which is equivalent to the empty list).
Thanks,
Stefan Kangas
- bug#36418: 26.2.90; mapconcat "SEPARATOR must be a string." is incorrect,
Stefan Kangas <=