Re: [External] : Re: How to make M-x TAB not work on (interactive) declaration?

[Nick Dokos]

<tomas@tuxteam.de> writes:

> On Mon, Jan 16, 2023 at 12:08:33AM +0300, Jean Louis wrote:
>> * Rudolf Adamkovič <salutis@me.com> [2023-01-15 23:27]:
>> > Jean Louis <bugs@gnu.support> writes:
>> > 
>> > >> (+) ➜ 0
>> > >
>> > > Why? It is wrong.
>> > 
>> > In Lisp, the `+' operator returns the sum of the additive identity with 
>> > all of
>> > its arguments.  The additive identity equals zero and you provided zero
>> > arguments.  Hence, you get the additive identity.
>> 
>> Send me references on what is additive identity.
>
> Identity element [0] as defined in group theory [1].
>
> The association of 0 with + and 1 with * runs deeper in maths
> than you think.
>
>> Though that it is so, it does not answer why is it so.
>
> Those are, of course, conventions. As whether the natural
> numbers begin with 0 or 1. But the above is, AFAIK, most
> widespread among mathematicians, wheter the latter is not.
>
> Cheers
>
> [0] https://en.wikipedia.org/wiki/Identity_element
> [1] https://en.wikipedia.org/wiki/Group_theory

The "empty sum" and "empty product" conventions are described in the
corresponding articles in Wikipedia too - they might help:

   https://en.wikipedia.org/wiki/Empty_sum
   https://en.wikipedia.org/wiki/Empty_product
   
-- 
Nick