Re: emacs-27 eebfb72 1/2: Document constant vs mutable objects better

[Michael Heerdegen]

Štěpán Němec <address@hidden> writes:

> Regarding comparing two equal floats, strings or lists by `eq', you warn
> about its undefinedness ("might not return nil") repeatedly, but can you
> give an actual example where (eq 1.2 1.2) or (eq "string" "string")
> returns non-nil in Elisp?

(eq "" "") => t.  You don't even have to compile.

> Otherwise, isn't it too hypothetical/theoretical to talk about in the
> manual?

It is important.  This once bit me, and it took a long time until I
found out what was wrong.  I had to ask here (AFAIR that's the reason
why an explanation was added to the manual).  And it was not code to
provoke that kind of thing.


Michael.