Path: utzoo!mnetor!uunet!husc6!bbn!bbn.com!mesard
From: mesard@bbn.com (Wayne Mesard)
Newsgroups: comp.bugs.4bsd
Subject: Re: csh arithmetic bug
Message-ID: <23216@bbn.COM>
Date: 11 Apr 88 13:27:09 GMT
References: <23570@ucbvax.BERKELEY.EDU>
Sender: news@bbn.COM
Lines: 31

From article <23570@ucbvax.BERKELEY.EDU>, by ph@miro.Berkeley.EDU (Paul Heckbert):
> Beware of doing arithmetic in csh, it's buggy!
> 
> The command	@ x = 0 - 1 + 2		sets x to -3	(should be 1)
> 
> The command	@ x = 0 - 1 - 2		sets x to 1	(should be -3)
> 
> (same error with Sun UNIX 3.5 on Sun3 and 4.3 BSD on Vax780)
> 
> csh must be parsing right-associatively by mistake!
> Division has a similar problem.
> 
> It's hard to believe that a bug like this would persist for 8 years.
> 

From csh(1):
:Expressions and Operators
:[...]
:     *   /   %
:          multiplication, division, remainder  (These  are  right
:          associative,  which  can  lead  to  unexpected results.
:          Group combinations explicitly with parentheses.)
:     +   -
:          addition, subtraction (also right associative)

It looks like a bug, it acts like a bug, but if it's documented...


-- 
unsigned *Wayne_Mesard();                     MESARD@BBN.COM
                                              BBN Labs, Cambridge, MA