Re: (*) -> 1

[Jean Louis]

* Michael Heerdegen <michael_heerdegen@web.de> [2023-01-17 18:58]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > Convention in multiplication is that there must be two numbers, that
> > is not followed, something else is followed.
> 
> There is no such convention.

Every elementary school is there to prove that convention of having at
least two addends for addition and two factors for multiplication
exists.

Thus, sorry, you reality does not correspond to mine.

There is no elementary school and I know many of them where pupils
would learn how in absence of any factor one shall count 1.

By chance, I am providing roomt to mathematics teacher who was not
introduced to this discussion, and I just called him and asked him if
there is anything that he knows that in absence of factors, the
multiplication operation would yield with anything, and he has no idea
what we are talking about.

What idea he has is that there must be 2 known factors for
multiplications and similar for addition.

That there may be some convention is not excluded, and that there is
identity element in mathematics is fine, but even the page of identity
element does not speak of creation of identity elements, but of usage
of identity elements.

Then we have contradiction that description of functions `*' and `+'
and `-' does not speak of any sets or group theory. And we have people
speaking yes, group theory, sets. 

But not description of relation from sets to Lisp function, why?

> You don't listen to or don't understand what people write.  Could
> you please try to do that before continuing this discussion?  It
> doesn't seem to be the case that you are consulting the references
> that had been presented to you.  So why are you keeping asking?

> Sorry to be direct like this, but what you are doing had been quite
> unfriendly for a while now.

I am sorry for your feelings. Solution is simple, just do M-x doctor


I have not find a reference. And I do not ask if identity element
exists, neither if sets exists, etc.

I am asking why is it in (some) Lisps? It is so far contradictory to
explanation of what function is supposed to do.

I can really understand and imagine, vividly, how you get angered by
Jean Louis, who keep asking same question over again. No, I did not
understand it. I have tried search engines. Where else shall I ask?

Picolisp does not think same:

(apply '+ '(1 2 3))
-> 6

and

(+)
-> NIL

while in Emacs Lisp

(apply '+ '(1 2 3)) ➜ 6
(+) ➜ 0

That makes vague the answer to "why" that one has to use it in such
functions as `apply', as Picolisp obviously does not do that way.


-- 
Jean

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