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Path: utzoo!utcs!flaps
From: flaps@utcs.uucp (Alan J Rosenthal)
Newsgroups: net.lang.c
Subject: Re:  A simple non-portable expression tha
Message-ID: <1229@utcs.uucp>
Date: Fri, 9-May-86 04:25:07 EDT
Article-I.D.: utcs.1229
Posted: Fri May  9 04:25:07 1986
Date-Received: Fri, 9-May-86 04:40:39 EDT
References: <130@brl-smoke.ARPA> <2609@utcsri.UUCP> <972@dataioDataio.UUCP>
Reply-To: flaps@utcs.UUCP (Alan J Rosenthal)
Organization: University of Toronto
Lines: 21
Summary: 

In article <972@dataioDataio.UUCP> bright@dataio.UUCP (Walter Bright) writes:
>Different code for (L+I1)+I2 and L+(I1+I2) will only be generated if
>ints are smaller than longs.

This is strictly true, but it is not true that different code for (L+I1)+I2
and L+(I1+I2) will necessarily be generated if ints are smaller than longs.
(Besides which, it is unwise to assume this; see K&R p34...)

Anyway, the official K&R quote here is from page 185 which says:
	...[besides precedence rules] the order of evaluation of
	expressions is undefined.  ... Expressions involving a
	commutative and associative operator (*, +, &, |, ^) may
	be rearranged arbitrarily, even in the presence of parentheses;
	to force a particular order of evaluation an explicit
	temporary must be used.

So you see that the expressions (L+I1)+I2 and L+(I1+I2) are not necessarily
distinct (though not necessarily identical either).

Alan J Rosenthal
{linus|decvax}!utzoo!utcs!flaps, {ihnp4|allegra}!cbosgd!utcs!flaps