On Sun, 28 May 2017, Jean-Christophe Helary wrote:

>
>> On May 24, 2017, at 23:34, Clément Pit-Claudel <cpitclaudel@gmail.com> wrote:
>>
>>> I just realized today that concat did not come with optional separators (unlike mapconcat). Is there a reason for that ?
>>>
>>>> I just using mapconcat when I feel that need:
>>>>
>>>> Example:
>>>>
>>>> (mapconcat #'identity '("a" "b" "c") "|")  => "a|b|c"
>>>
>>> That's roughly the definition of string-join in subr-x:
>>>
>>> (defsubst string-join (strings &optional separator)
>>>  "Join all STRINGS using SEPARATOR."
>>>  (mapconcat 'identity strings separator))
>
> Would it be acceptable to provide separators to concat or is it preferable to use string-join instead?
The latter.
Func. `concat' accepts and arbitrary number of sequences (not a list of
sequences as `string-join').