Re: [PATCH v3] Allow applying filters to summary consecutively

[Eli Zaretskii]

> Date: Fri, 11 Nov 2022 18:00:06 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: rms@gnu.org, andrea.monaco@autistici.org, rpluim@gmail.com, 
>     emacs-devel@gnu.org
> 
> > That's okay, thanks.  But it's only the beginning of my problem.  How do 
> > you describe the effect of applying a filter on top of one or more other 
> > filters?  Andrea wants to use "intersection", but I tend to think this 
> > is too "mathematical" and too vague to explain clearly what happens. 
> > What would be a good terminology for that?
> 
> I think there are two possibilities when adding another filter: either 
> broadening the already existing filtering ("union" in mathematical terms) 
> or narrowing the already existing filtering ("intersection" in 
> mathematical terms).

It's what you call "intersection", obviously.