From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,a00006d3c4735d70
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2004-02-25 09:33:51 PST
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!nntp.abs.net!ash.uu.net!spool.news.uu.net!not-for-mail
Date: Wed, 25 Feb 2004 12:33:40 -0500
From: Hyman Rosen <hyrosen@mail.com>
User-Agent: Mozilla Thunderbird 0.5 (Windows/20040207)
X-Accept-Language: en-us, en
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Subject: Re: In-Out Parameters for functions
References: <1075987360.225622@master.nyc.kbcfp.com> <40236C0B.E988E003@0.0>
 <xay_b.429$ax2.177@nwrdny03.gnilink.net>
 <pan.2004.02.24.01.44.30.311621@email.ro>
 <1077634311.254581@master.nyc.kbcfp.com>
 <pan.2004.02.24.23.23.33.578111@email.ro>
 <mailman.20.1077669870.327.comp.lang.ada@ada-france.org>
 <pan.2004.02.25.09.01.17.858502@email.ro>
 <1077718871.47635@master.nyc.kbcfp.com>
 <54cp3095jmv8s17h63d4bjdus0tec7l7pt@jellix.jlfencey.com>
 <1077721343.481619@master.nyc.kbcfp.com>
 <ljgp301lgj3r0totpo3hlkmt3dbnbe0i33@jellix.jlfencey.com>
 <1077724400.221032@master.nyc.kbcfp.com>
 <slrnc3pjmj.l1h.randhol+valid_for_reply_from_news@k-083152.nt.ntnu.no>
 <1077728214.676718@master.nyc.kbcfp.com>
 <slrnc3plpv.lq0.randhol+valid_for_reply_from_news@k-083152.nt.ntnu.no>
In-Reply-To: 
 <slrnc3plpv.lq0.randhol+valid_for_reply_from_news@k-083152.nt.ntnu.no>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Organization: KBC Financial Products
Message-ID: <1077730428.46831@master.nyc.kbcfp.com>
Cache-Post-Path: master.nyc.kbcfp.com!unknown@nightcrawler.nyc.kbcfp.com
X-Cache: nntpcache 3.0.1 (see http://www.nntpcache.org/)
NNTP-Posting-Host: 204.253.250.10
X-Trace: 1077730428  6522 204.253.250.10
Xref: archiver1.google.com comp.lang.ada:5808
Date: 2004-02-25T12:33:40-05:00
List-Id: <comp.lang.ada>

Preben Randhol wrote:
> My point was that when you use the and then you tell the compiler to
> evaluate left-side before right. Whereas if you use only and it is not
> given which side will be evaluated first. At least I thought so.

Yes, that's correct. However, program behavior is always subject to
the "as if" convention. That is, the program must have observable
behavior as if the compiler did things in the order that the language
specified, but that observable behavior is limited by the language
definition to things like I/O, calling imported subprograms, and some
other stuff that can be loosely categorized as side-effects.

In the proposed case of (sqrt(x) > 0.5 and b), if sqrt(x) has side
effects it must be evaluated regardless of the value of b, and if
it has no side effects you cannot know if it has been evaluated, and
so the compiler may evaluate b first and never evaluate sqrt(x) at
all. The latter holds even if you write (sqrt(x) > 0.5 and then b).