Re: Appending to a list

["Óscar Fuentes" <ofv@wanadoo.es>]

Joost Kremers <joostkremers@fastmail.fm> writes:

> On Sun, Dec 13 2020, steve-humphreys@gmx.com wrote:
>> Would appending to list like this be good?
>>
>> (setq bird '("Toucan" "King Fisher"))
>> (setq bird (append bird ("Swift") ))
>
> This should result in an error, because `("Swift")` isn't quoted. You'd need:
>
>     (setq bird (append bird '("Swift")))
>
> But note that the last argument of `append` isn't copied, so it may not be a
> good idea to use a literal list.
>
>> Or does one customarily use other constructs for
>> adding to a list?
>
> `push` is what I would use:
>
>     (push "Swift" bird)

This does not append.

> No need to use `setq` here.
>
> `push` won't check if the element is already in the list, though. You can use
> `cl-pushnew` in that case, but be sure to load the library it's in:
>
>     (require 'cl-lib)
>     (cl-pushnew "Swift" bird)

Isn't that the same as

(add-to-list bird "Swift" t)

?