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Article #9605Re: Portable Languages (was: Expression sequencing query)
From: Jason Zions
Date: Thu, 16 Oct 1986 17:33
Date: Thu, 16 Oct 1986 17:33
27 lines
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1742 bytes
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.
--
This is not an official statement of Hewlett-Packard Corp., and does not
necessarily reflect the views of HP. It is provided completely without warranty
of any kind. Lawyers take 3d10 damage and roll a saving throw vs. ego attack.
Jason Zions Hewlett-Packard
Colorado Networks Division 3404 E. Harmony Road
Mail Stop 102 Ft. Collins, CO 80525
{ihnp4,seismo,hplabs,gatech}!hpfcdc!hpcnoe!jason
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!watmath!clyde!caip!rutgers!husc6!mit-eddie!genrad!decvax!ucbvax!hplabs!hpcea!hpfcdc!hpcnoe!jason 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