bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

[Van Ly via Bug reports for GNU Emacs, the Swiss army knife of text editors]

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Hello,

The following calculation errors in elisp.

  ELISP> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
  *** Eval error ***  Arithmetic error

The SBCL repl doesn't.

  CL-USER> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
  63/65 (0.9692308, 1260/13%)

Steps to reproduce the error.

  1. start using, 'emacs -Q'
  2. get to the ielm elisp prompt, 'M-x ielm'
  3. enter the above calculation


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In GNU Emacs 29.0.92 (build 1, aarch64-unknown-linux-gnu, GTK+ Version
 3.24.24, cairo version 1.16.0) of 2023-06-21 built on x23
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

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bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

[Stephen Berman]

On Mon, 3 Jul 2023 16:20:34 GMT Van Ly via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org> wrote:

> Hello,
>
> The following calculation errors in elisp.
>
>   ELISP> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
>   *** Eval error ***  Arithmetic error
>
> The SBCL repl doesn't.
>
>   CL-USER> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
>   63/65 (0.9692308, 1260/13%)
>
> Steps to reproduce the error.
>
>   1. start using, 'emacs -Q'
>   2. get to the ielm elisp prompt, 'M-x ielm'
>   3. enter the above calculation

`/' in Elisp is different from `/' in Common Lisp.

(elisp) Arithmetic Operations:

  If all the arguments are integers, the result is an integer,
  obtained by rounding the quotient towards zero after each division.

Hence (/ 3 4), (/ 7 13) and (/ 5 12) all evaluate to 0, and "If you
divide an integer by the integer 0, Emacs signals an ‘arith-error’
error".

But in Common Lisp
(http://www.lispworks.com/documentation/HyperSpec/Body/f_sl.htm):

  If each argument is either an integer or a ratio, and the result is
  not an integer, then it is a ratio.

Hence (/ 3 4) => 3/4,  (/ 7 13) => 7/13 and (/ 5 12) => 5/12

Steve Berman

bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

[Eli Zaretskii]

> Date: Mon, 3 Jul 2023 16:20:34 GMT
> From:  Van Ly via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> The following calculation errors in elisp.
> 
>   ELISP> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
>   *** Eval error ***  Arithmetic error

You are dividing zero by zero.

This is not a bug.

> The SBCL repl doesn't.

Emacs is not SBCL.

bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

[Van Ly via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> From: Stephen Berman
>
> `/' in Elisp is different from `/' in Common Lisp.
> 
> (elisp) Arithmetic Operations:
> 
>   If all the arguments are integers, the result is an integer,
>   obtained by rounding the quotient towards zero after each division.
> 
> Hence (/ 3 4), (/ 7 13) and (/ 5 12) all evaluate to 0, and "If you
> divide an integer by the integer 0, Emacs signals an ‘arith-error’
> error".
> 
> But in Common Lisp
> (http://www.lispworks.com/documentation/HyperSpec/Body/f_sl.htm):
> 
>   If each argument is either an integer or a ratio, and the result is
>   not an integer, then it is a ratio.
> 
> Hence (/ 3 4) => 3/4,  (/ 7 13) => 7/13 and (/ 5 12) => 5/12
> 

Thank you Steve.

bug#64441: 29.0.92; elisp arithmetic error at ielm prompt

[Stefan Kangas]

tags 64441 + notabug
close 64441
thanks

Eli Zaretskii <eliz@gnu.org> writes:

>>   ELISP> (/ (* (/ 3 4) (/ 7 13)) (/ 5 12))
>>   *** Eval error ***  Arithmetic error
>
> You are dividing zero by zero.
>
> This is not a bug.

Yup, so I'm closing it.