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Re: (*) -> 1
From: |
Jean Louis |
Subject: |
Re: (*) -> 1 |
Date: |
Fri, 20 Jan 2023 19:06:41 +0300 |
User-agent: |
Mutt/2.2.9+54 (af2080d) (2022-11-21) |
* Tassilo Horn <tsdh@gnu.org> [2023-01-20 16:14]:
> Jean Louis <bugs@gnu.support> writes:
>
> >> Yes, and I think it's seriously wrong with
> >>
> >> : (+)
> >> -> NIL
> >>
> >> where its docs say
> >>
> >> Returns the sum of all num arguments. When one of the arguments
> >> evaluates to NIL, it is returned immediately.
> >
> > For some reason PicoLisp is quite different than other Lisp. I have
> > asked author about it.
> >
> > 15:09 <abu[m]> It is a "feature" that NIL propagates through
> > arithmetics
>
> Well, but with (*) and (+), there is no single NIL involved! And in
> Elisp (+ nil), where actually a nil is involved, you get an error.
What we can learn from PicoLisp is that there was no use for (*) ➜ 1
and that programs work, GUI applications and Android/Replicant work,
and there was no use of (*) ➜ 1 so far.
Similarly like author of PicoLisp finding use when (*) ➜ NIL, so I
would also find (very rare) use with errors. Even if NIL, I find use
as I will get error raised in combinations like (+ (*) (* 2 2)),
because (+ nil 4) would raise error.
> > 15:09 <jmarciano> How does it help instead of providing identity
> > elements?
> > 15:09 <abu[m]> (*) especially was not contemplated though, it is a
> > pretty useless call
> > [...]
> > 15:12 <abu[m]> What is a call like (*) useful for?
> >
> > As you see, author also asked naturally why is it useful.
>
> So go and ask why he thinks (apply '+ ()) -> NIL is more useful than 0
> given that the sum of the empty set of numbers _is_ 0.
I will ask.
But docstring does not speak of empty sets. You introduce "sets" where
there is not direct relation to it.
(+ &rest NUMBERS-OR-MARKERS)
Return sum of any number of arguments, which are numbers or
markers. Of course I get confused.
I ask A, but people say B.
I ask A, but people say C.
I ask A, but people say D.
No answer about A. But there are many introductions of things not
relevant to function itself.
I still believe that there is some actual practical use.
`apply' can be used with (apply '+ '(a b)) as why would you need in
apply for addition two arguments?
If list is with one argument, testing with `cadr' will be known,
otherwise, I use `car' instead of `apply'.
> >> So why does it return NIL? And why do you apparently consider that
> >> useful? And can something be useful even though it is incorrect?
> >
> > I find it right as with error raising or nil I can find what is
> > wrong.
>
> It's good to signal an error when the expression is wrong as does Elisp
> with
>
> (+ nil)
> (* 1 2 nil)
> (apply #'+ (list 1 nil 19))
> (+ 2 "i am not a number")
That is exactly my point, what you see useful there, I see too. Making
it less error prone with useless default identity elements hides the
real event preceding the operation.
--
Jean
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- Re: (*) -> 1, Jean Louis, 2023/01/19
- Re: (*) -> 1, Jean Louis, 2023/01/19
- Re: (*) -> 1, Jean Louis, 2023/01/20
- Re: (*) -> 1, Tassilo Horn, 2023/01/20
- Re: (*) -> 1, Jean Louis, 2023/01/20
- Re: (*) -> 1, Tassilo Horn, 2023/01/20
- Re: (*) -> 1,
Jean Louis <=
- Re: (*) -> 1, Tassilo Horn, 2023/01/21
- Re: (*) -> 1, Emanuel Berg, 2023/01/22
- Re: (*) -> 1, Jean Louis, 2023/01/22
- Re: (*) -> 1, Emanuel Berg, 2023/01/22
- RE: [External] : Re: (*) -> 1, Drew Adams, 2023/01/22
- Re: (*) -> 1, Akib Azmain Turja, 2023/01/22
- Re: (*) -> 1, Emanuel Berg, 2023/01/22
- Re: (*) -> 1, Jean Louis, 2023/01/23
- Re: (*) -> 1, Jean Louis, 2023/01/23
- Re: (*) -> 1, Emanuel Berg, 2023/01/23