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!news1.google.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: "Tom Linden" Newsgroups: comp.lang.ada,comp.lang.fortran,comp.lang.pl1 Subject: Re: Ada vs Fortran for scientific applications Date: Tue, 11 Jul 2006 08:35:40 -0700 Organization: Kednos Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 Content-Transfer-Encoding: Quoted-Printable X-Trace: individual.net Tr6o5gYiqtfqkLk3QmIcvQ2vvWZpsM7EyoGQ4KqfFe5ggs1ZJC User-Agent: Opera Mail(BETA2)/9.00 (Win32) Xref: g2news2.google.com comp.lang.ada:5617 comp.lang.fortran:11942 comp.lang.pl1:1984 Date: 2006-07-11T08:35:40-07:00 List-Id: On Tue, 11 Jul 2006 08:02:47 -0700, wrote: > > "Tom Linden" wrote in message > news:op.tci16qgszgicya@hyrrokkin... > On Mon, 10 Jul 2006 23:46:45 -0700, 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. > > TL>In general, this is not possible, and it is somewhat silly to have = the > TL>compiler issue such messages, because on the average it will be > TL>wrong as often as it is right. This can not be done at compile-ti= me > TL>but must be done at run-time and it requires the compiler to > TL>generate a lot of machinery to produce such mediocre messages. > TL>Wht we did in PL/I was to produce in the cross-reference > TL>listing information on where a variable was referenced or > TL>assigned, but this was also somewhat incomplete because > TL>it requires a further analysis of aliasing. My view is that it is= > TL>of dubious value. > TL> > > It might be of dubious value in PL/I, but it is quite helpful > in Ada. These warnings often help with better structuring of a > program. In a large, complex program, they prevent errors that > result from simple little oversights we all make in the normal > course of programming. > > These kinds of warnings extend to methods declared, but never > invoked. For example, in the sample code in the earlier post, > if I had never used Ada.Integer_Text_IO in my program, the > compiler would have informed me that I had a package in > scope that I never used. I have never known the compiler > to issue a message that was wrong. On the other hand, > it is a warning, not a fatal error because I really might want > to use that artifact in a future iteration of my development. > When I do use it, the warning goes away. I personally > find this very helpful. Others may find it annoying. In > the long run, it is a good feature when developing > safety-critical software where extraneous code is not a > good thing. My comments were not restricted to PL/I, but apply generally to any compiler, and specifically Ada was intended. Since I had put in the scaffolding for producing the info in cross reference listings I also played with generating precisely the sort of warnings that you refer to, but found it generated too much "clutter" of questionable value. That was my view, FWIW > > Richard Riehle > > >