Strange division using mixed integers and floats

Strange division using mixed integers and floats

[Johan Bockgård]

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In GNU Emacs 21.2.1 (sparc-sun-solaris2.8, X toolkit)
 of 2002-09-24 on nob.dd.chalmers.se
configured using `configure  --x-includes=/opt/pd/include/ --x-libraries=/opt/pd/lib --prefix=/rec/emacs-21.2/'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: iso_8859_1
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

Ok, I know why this happens:

(/ 5 4) => 1

But this behaviour is *highly* confusing:

(/ 5 4 2.3) => 0.4347826086956522

Cf. (/ 5 4.0 2.3) => 0.5434782608695653

At least there should be a warning in the manual.

Recent input:
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ESC O B ESC O B ESC O B C-l ESC O A ESC O A ESC O A 
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-- 
Johan Bockgård

Re: Strange division using mixed integers and floats

[Kevin Rodgers]

Johan Bockga*rd wrote:
 > Ok, I know why this happens:
 >
 > (/ 5 4) => 1
 >
 > But this behaviour is *highly* confusing:
 >
 > (/ 5 4 2.3) => 0.4347826086956522
 >
 > Cf. (/ 5 4.0 2.3) => 0.5434782608695653
 >
 > At least there should be a warning in the manual.

*** elisp-manual-21-2.8/numbers.texi.orig	Sat Sep  8 11:42:52 2001
--- elisp-manual-21-2.8/numbers.texi	Tue Apr 27 09:45:26 2004
***************
*** 541,547 ****
   divides @var{dividend} by each divisor in turn.  Each argument may be a
   number or a marker.

! If all the arguments are integers, then the result is an integer too.
   This means the result has to be rounded.  On most machines, the result
   is rounded towards zero after each division, but some machines may round
   differently with negative arguments.  This is because the Lisp function
--- 541,548 ----
   divides @var{dividend} by each divisor in turn.  Each argument may be a
   number or a marker.

! If both of the arguments are integers, then the result---the
! intermediate result, if there are additional arguments---is an integer too.
   This means the result has to be rounded.  On most machines, the result
   is rounded towards zero after each division, but some machines may round
   differently with negative arguments.  This is because the Lisp function

-- 
Kevin Rodgers