GNU bug report logs - #923
In CVS Emacs, calc-eval gives multiplication higher precidence than division

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Package: emacs;

Reported by: Stefan Monnier <monnier <at> iro.umontreal.ca>

Date: Sun, 7 Sep 2008 21:25:05 UTC

Severity: normal

Merged with 914, 915, 918, 920, 921, 924, 928, 929, 930, 932, 933, 934, 937, 941, 944

Done: Chong Yidong <cyd <at> stupidchicken.com>

Bug is archived. No further changes may be made.

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Report forwarded to bug-submit-list <at> lists.donarmstrong.com, Emacs Bugs <bug-gnu-emacs <at> gnu.org>:
bug#923; Package emacs. Full text and rfc822 format available.
Acknowledgement sent to Stefan Monnier <monnier <at> iro.umontreal.ca>:
New bug report received and forwarded. Copy sent to Emacs Bugs <bug-gnu-emacs <at> gnu.org>. Full text and rfc822 format available.

Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: jay.p.belanger <at> gmail.com
Cc: bug-gnu-emacs <at> gnu.org, Francis Litterio <flitterio <at> gmail.com>,
        emacs-devel <at> gnu.org
Subject: Re: In CVS Emacs, calc-eval gives multiplication higher precidence than division
Date: Sun, 07 Sep 2008 17:15:38 -0400

>>> That's not a bug.  While many systems give division a higher precendence
>>> than multiplication, that isn't a universal rule.
>> Actually, I don't know of any system that gives higher precedence to
>> division.

> According to Wikipedia:
>   An expression like 1/2x is interpreted as 1/(2x) by TI-82, but as
>   (1/2)x by TI-83. While the first interpretation may be expected by
>   some users, only the latter is in agreement with the standard rules
>   stated above. 

That could be due to a higher precedence, but could also be due to an
equal precedence together with left-associativity.  Given that (a*b)/c
is often mathematically equal to a*(b/c), the difference is generally
hard to see, unless rounding comes into play.

All textbooks and language references I know use the "equal precedence
and left associativity" rule rather than giving higher precedence to
the division.

>> The general rule that (AFAIK) all programming languages
>> follow (other than those that don't use infix-with-precedence, such as
>> Lisp and Smalltalk) is that * and / have the same precedence (and are
>> left associative).

> That behavior is available, but you have to ask for it by setting
> `calc-multiplication-has-precedence' to nil.

I know.  But we're talking about the default behavior.


        Stefan
Forcibly Merged 914 915 918 920 921 923 924. Request was from Glenn Morris <rgm <at> gnu.org> to control <at> emacsbugs.donarmstrong.com. (Mon, 08 Sep 2008 02:25:06 GMT) Full text and rfc822 format available.
Forcibly Merged 914 915 918 920 921 923 924 928 929 930. Request was from Glenn Morris <rgm <at> gnu.org> to control <at> emacsbugs.donarmstrong.com. (Mon, 08 Sep 2008 20:35:04 GMT) Full text and rfc822 format available.
Forcibly Merged 914 915 918 920 921 923 924 928 929 930 932 933. Request was from Glenn Morris <rgm <at> gnu.org> to control <at> emacsbugs.donarmstrong.com. (Mon, 08 Sep 2008 21:00:06 GMT) Full text and rfc822 format available.
Forcibly Merged 914 915 918 920 921 923 924 928 929 930 932 933 934. Request was from Glenn Morris <rgm <at> gnu.org> to control <at> emacsbugs.donarmstrong.com. (Mon, 08 Sep 2008 21:00:09 GMT) Full text and rfc822 format available.
Forcibly Merged 914 915 918 920 921 923 924 928 929 930 932 933 934 937. Request was from Glenn Morris <rgm <at> gnu.org> to control <at> emacsbugs.donarmstrong.com. (Mon, 08 Sep 2008 22:30:04 GMT) Full text and rfc822 format available.
Forcibly Merged 914 915 918 920 921 923 924 928 929 930 932 933 934 937 941 944. Request was from "Juanma Barranquero" <lekktu <at> gmail.com> to control <at> emacsbugs.donarmstrong.com. (Tue, 09 Sep 2008 14:50:07 GMT) Full text and rfc822 format available.
bug archived. Request was from Debbugs Internal Request <don <at> donarmstrong.com> to internal_control <at> emacsbugs.donarmstrong.com. (Wed, 08 Oct 2008 14:24:03 GMT) Full text and rfc822 format available.
This bug report was last modified 16 years and 255 days ago.

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