GNU bug report logs - #75170
add-to-alist: new function

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Roland Winkler <winkler <at> gnu.org>
Cc: 75170 <at> debbugs.gnu.org, rpluim <at> gmail.com, acorallo <at> gnu.org, stefankangas <at> gmail.com, monnier <at> gnu.org
Subject: bug#75170: add-to-alist: new function
Date: Tue, 21 Jan 2025 21:35:05 +0200

> From: Roland Winkler <winkler <at> gnu.org>
> Cc: Stefan Kangas <stefankangas <at> gmail.com>,  rpluim <at> gmail.com,
>   acorallo <at> gnu.org,  75170 <at> debbugs.gnu.org,  monnier <at> gnu.org
> Date: Tue, 21 Jan 2025 13:21:01 -0600
> 
> On Tue, Jan 21 2025, Eli Zaretskii wrote:
> > Can someone tell me again why add-to-list doesn't fit the bill of
> > being a tool easy for end-users?  I've been using it in my init files
> > to customize stuff like default-frame-alist since about forever.
> 
> The following was my answer from end of last year:
> 
> On Sun, Dec 29 2024, Roland Winkler wrote:
> > The advantage I see for also having the function add-to-alist is the
> > following:
> >
> > add-to-list checks for the presence of an element in a list.  In the
> > case of alists, this means it checks for the presence of associations.
> > You cannot easily modify an existing association with add-to-list.  If
> > you have an alist with association (foo . bar) and you call add-to-list
> > with an element (foo . baz), add-to-list will not remove the association
> > (foo . bar), but the alist will then contain both associations.
> >
> > add-to-alist checks for the presence of keys and it makes sure that each
> > key appears only once in an alist.  By default, it replaces the value of
> > an existing key.  This makes it easy to modify an existing association.
> > Only with the optional arg NO-REPLACE non-nil, it will preserve an
> > existing association.

I know all this, but why do we think end-users who aren't comfortable
with alist-get and setf will need to "check for the presence of keys
and make sure that each key appears only once in an alist"?  Since by
default add-to-list prepends the new association, those which come
after it don't matter, right?

So if we want to cater to people for whom Lisp is not a first
language, why do we think they need anything beyond add-to-list?  Does
the fact that I still use add-to-list, so many years after I started
using Emacs, tell something?

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