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 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,c4cb2c432feebd9d X-Google-Thread: 1094ba,c4cb2c432feebd9d X-Google-Thread: 101deb,15c6ed4b761968e6 X-Google-Attributes: gid103376,gid1094ba,gid101deb,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news3.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!nx01.iad01.newshosting.com!newshosting.com!69.28.186.75.MISMATCH!hwmnpeer01.lga!news.highwinds-media.com!hw-filter.lga!fe11.lga.POSTED!53ab2750!not-for-mail From: "John W. Kennedy" User-Agent: Thunderbird 1.5.0.4 (Windows/20060516) MIME-Version: 1.0 Newsgroups: comp.lang.ada,comp.lang.fortran,comp.lang.pl1 Subject: Re: Ada vs Fortran for scientific applications References: <0ugu4e.4i7.ln@hunter.axlog.fr> <%P_cg.155733$eR6.26337@bgtnsc04-news.ops.worldnet.att.net> <6H9dg.10258$S7.9150@news-server.bigpond.net.au> <1hfv5wb.1x4ab1tbdzk7eN%nospam@see.signature> <2006052509454116807-gsande@worldnetattnet> <1kzktalo9krea$.z8n9wev45xct$.dlg@40tude.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Message-ID: Date: Tue, 11 Jul 2006 10:46:04 -0400 NNTP-Posting-Host: 68.193.246.216 X-Complaints-To: abuse@cv.net X-Trace: fe11.lga 1152629200 68.193.246.216 (Tue, 11 Jul 2006 07:46:40 MST) NNTP-Posting-Date: Tue, 11 Jul 2006 07:46:40 MST Organization: Optimum Online Xref: g2news2.google.com comp.lang.ada:5611 comp.lang.fortran:11933 comp.lang.pl1:1978 Date: 2006-07-11T10:46:04-04:00 List-Id: adaworks@sbcglobal.net wrote: > "robin" wrote in message > news:z9Dsg.2740$tE5.2374@news-server.bigpond.net.au... >> Compilers can check for uninitialized variables during compilation. >> > True. In fact, Ada compilers issue a warning for any variable > that is used before a value is assigned to it. If a parameter is > included in a method (function/procedure/subroutine) and never > referenced, a warning is issued. Sometimes the pragma > Normalize_Scalars is useful. Often, the correct design is to > leave variables uninitialized until they are used so an exception > can be raised. However, since the compiler will emit a warning > about variables that have never been assigned a value in an algorithm > that tries to use it, no harm is really done since the careful programmer > will not release a program with warnings in it. > > So, I am assuming, Robin, that PL/I does something similar: a warning > for any variable that is used in a program before a value is assigned to it. Smart compilers may try to do so, as a by-product of optimization, but PL/I is too old a design for this sort of thing to be taken for granted; there are unavoidable holes, because PL/I A) passes by reference, B) does not have in-out parameter declaration, and C) uses separate compilation and a dumb linker, making global flow analysis impossible. (Java is the only language I know of that will actually fail the compile unless it /knows/ that every variable is initialized before use in every possible path.) -- John W. Kennedy "The blind rulers of Logres Nourished the land on a fallacy of rational virtue." -- Charles Williams. "Taliessin through Logres: Prelude"