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: 103376,25aa3c7e1b59f7b5
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2002-01-04 11:09:44 PST
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!skynet.be!skynet.be!newspeer.radix.net!uunet!ash.uu.net!spool0900.news.uu.net!reader0902.news.uu.net!not-for-mail
Message-ID: <3C35FE2A.9020802@mail.com>
Date: Fri, 04 Jan 2002 14:10:34 -0500
From: Hyman Rosen <hyrosen@mail.com>
User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US;
 rv:0.9.7+) Gecko/20010929
X-Accept-Language: en-us
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Subject: Re: A case where Ada defaults to unsafe?
References: <3C34BF2C.6030500@mail.com> <a12il6$gcs$1@bob.news.rcn.net>
 <3C34D252.4070307@mail.com> <5ee5b646.0201040829.18db8001@posting.google.com>
 <3C35E733.6030603@mail.com> <u3bu42jp7h5k0d@corp.supernews.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Organization: KBC Financial Products
Cache-Post-Path: master.nyc.kbcfp.com!unknown@mosquito.nyc.kbcfp.com
X-Cache: nntpcache 2.3.3 (see http://www.nntpcache.org/)
NNTP-Posting-Host: 204.253.250.10
X-Trace: 1010171382 reader2.ash.ops.us.uu.net 10844 204.253.250.10
Xref: archiver1.google.com comp.lang.ada:18556
Date: 2002-01-04T14:10:34-05:00
List-Id: <comp.lang.ada>

Matthew Heaney wrote:

> But you have to know that.  How is learning the difference between "&" and
> "&&" any different from learning the difference between "and" and "and
> then"?


"&" does integer bit combinations, while "&&" does a boolean
conjunction on (lhs != 0) and (rhs != 0), short-circuiting as
needed. The operations are totally different.

On the other hand, "and" and "and then" perform the same logical
operation. To use "and", the programmer must make a decision that
the order of evaluation of the operands doesn't matter. If he is
wrong, he has introduced a subtle bug. If he is right, he has
gained nothing over using "and then".