Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ncar!ico!ism780c!news
From: news@ism780c.isc.com (News system)
Newsgroups: comp.lang.c
Subject: Re: () ignored in some expressions
Message-ID: <41297@ism780c.isc.com>
Date: 13 Apr 90 00:48:58 GMT
References: <48079@lanl.gov> <1272@sdrc.UUCP>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 21

In article <1272@sdrc.UUCP> scjones@sdrc.UUCP (Larry Jones) writes:
>In article <48079@lanl.gov>, u096000@lanl.gov (Roger A. Cole) writes:
>> In K&R1, expressions involving one of the associative and commutative
>> operators can be arranged even when parenthesized.
>
>Well, if the operators ARE commutative and associative, it
>doesn't make any difference!  In the environment the C grew up
>in, integer arithmetic overflows wrap around without producing
>any exceptions, so the integer operators really are associative
>and commutative.

A common misconception.  Integer operators are associaive for add and
subtract but not for multiply and divide.  for example:

    long x=70000;
    x*(x/x);   /* 700000 if parens are honored */
    (x*x)/x;   /* 8643   if parens are honered */

The above assumes longs are 32 bits.

    Marv Rubinstein