Bug 10578 - [xcalc] uses wrong order of operations in infix mode
Summary: [xcalc] uses wrong order of operations in infix mode
Status: RESOLVED INVALID
Alias: None
Product: xorg
Classification: Unclassified
Component: App/other (show other bugs)
Version: 7.2 (2007.02)
Hardware: Other All
: medium normal
Assignee: Matthieu Herrb
QA Contact: Xorg Project Team
URL: http://bugs.debian.org/cgi-bin/bugrep...
Whiteboard: 2011BRB_Reviewed
Keywords: love
Depends on:
Blocks:
 
Reported: 2007-04-09 11:17 UTC by Brice Goglin
Modified: 2018-06-12 19:10 UTC (History)
1 user (show)

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Description Brice Goglin 2007-04-09 11:17:29 UTC
Bug reported by Maciej Kalisiak on the Debian BTS 6 years ago, still applies to latest xcalc:

It appears there's a horrible (in that xcalc is potentially misleading SO MANY
users with wrong results) bug in the way it does order of operations in the
"infix" mode.  Consider:
	2*3-3*2+1=
	
The solution, if we are to follow order of operations, is +1.  xcalc reports
-1.

I took a peek at the code, and the problem seems to be in math.c, in equf().
It computes the final solution by performing the remaining calculations (at
this point the multiplications have been performed and the results pushed on
the number stack) from RIGHT TO LEFT, no matter what, which is just plain
wrong.  In the specific example it's computing:
	6-6+1
as
	6-(6+1)

Reversing the direction of the final computation is not the correct solution
either.  Consider
	2*3-3*2*3
When the '=' is pressed, the expression that equf() gets to evaluate, I think,
will be:
	6-6*3
which should be done in right to left order.

Overall the mechanism for doing infix calculation in xcalc seems to be
seriously broken.
Comment 1 Adam Jackson 2018-06-12 19:10:34 UTC
Mass closure: This bug has been untouched for more than six years, and is not
obviously still valid. Please reopen this bug or file a new report if you continue to experience issues with current releases.


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