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From: jason@hpcnoe.UUCP (Jason Zions)
Newsgroups: net.lang.c
Subject: Re: Portable Languages (was: Expression sequencing query)
Message-ID: <790007@hpcnoe.UUCP>
Date: Thu, 16-Oct-86 13:33:21 EDT
Article-I.D.: hpcnoe.790007
Posted: Thu Oct 16 13:33:21 1986
Date-Received: Tue, 21-Oct-86 21:50:41 EDT
References: <4504@brl-smoke.ARPA>
Organization: HP Colorado Networks Division
Lines: 27

dik@mcvax.uucp (Dik T. Winter) writes:
> And so should it.  Once I required the expression (A - B) - C evaluated
> exactly that way.  It didn't do so.  However, after removing the
> parenthesis it was evaluated the way I wanted.  Counterintuitive?

Not counterintuitive - BROKEN. Although C may rearrange the order of
evaluation with respect to + * & ^ and |, it may not do so w.r.t. operators
which aren't associative and commutative.

Rearranging (A - B) - C is just plain wrong.

References:
H&S Section 7.11, page 190
K&R Section 2.12, page 49

Note that both references state that reordering is permitted only for the
associative and commutative operators; they do not mention the names of the
operators for which reordering is forbidden.
--
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Jason Zions				Hewlett-Packard
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