* Fixed point design error in Ada95 @ 1998-09-09 0:00 Wayne Magor 1998-09-10 0:00 ` Tucker Taft 0 siblings, 1 reply; 20+ messages in thread From: Wayne Magor @ 1998-09-09 0:00 UTC (permalink / raw) I don't follow this newsgroup regularly, so I'm sorry if this topic has been discussed to death already. I'd like to know if there is a plan to fix the design error in Ada95 that prevents user overloading of the "*" and "/" operators for fixed-point types (it results in an ambiguity on the call)? The last I heard, the GNAT compiler did not implement fixed-point correctly (as per the Ada95 spec) so this wasn't a problem for that compiler. Is that true? Can other compilers do the same? I had heard that this problem was known and was being discussed over a year ago. Was there a resolution, or is it being deferred to the next version of Ada? Is there a web site that contains Ada language issues such as this? Also, what is the name of the Ada language maintenance committee? Thanks, Wayne. ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-09 0:00 Fixed point design error in Ada95 Wayne Magor @ 1998-09-10 0:00 ` Tucker Taft 1998-09-10 0:00 ` dewarr 1998-09-11 0:00 ` Fixed point design error in Ada95 Wayne Magor 0 siblings, 2 replies; 20+ messages in thread From: Tucker Taft @ 1998-09-10 0:00 UTC (permalink / raw) Wayne Magor (wemagor@sym1.cca.rockwell.com_nospam) wrote: : I don't follow this newsgroup regularly, so I'm sorry if this topic has : been discussed to death already. : I'd like to know if there is a plan to fix the design error in Ada95 that : prevents user overloading of the "*" and "/" operators for fixed-point : types (it results in an ambiguity on the call)? No solution has been defined. The best workaround is to use names other than "*" and "/" for user-defined multiply and divide operations for fixed-point types. You can overload the predefined "*" and "/" for the type of interest with an "abstract" definition to make it less likely they get misused. : ... The last I heard, the : GNAT compiler did not implement fixed-point correctly (as per the Ada95 : spec) so this wasn't a problem for that compiler. Is that true? Can : other compilers do the same? This seems like the wrong solution. We did discuss various explicit pragmas to get Ada-83 compatible behavior, but I don't believe it went anywhere. : I had heard that this problem was known and was being discussed over a : year ago. Was there a resolution, or is it being deferred to the next : version of Ada? : Is there a web site that contains Ada language issues such as this? www.adaic.org has an archive of comments. If you have your own comments, you can send them to ada9x-mrt@inmet.com, where they will get logged, and redistributed to all interested parties once a day. The format for comments is given in the Reference Manual. You can also get yourself added to the "interested parties" list by sending mail to stt@inmet.com. : Also, what is the name of the Ada language maintenance committee? The Ada Rapporteur Group, which is part of ISO Working Group 9 (WG9) : Thanks, : Wayne. -- -Tucker Taft stt@inmet.com http://www.inmet.com/~stt/ Intermetrics, Inc. Burlington, MA USA An AverStar Company ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-10 0:00 ` Tucker Taft @ 1998-09-10 0:00 ` dewarr 1998-09-10 0:00 ` Wayne Magor 1998-09-11 0:00 ` GNAT Professional ? Mats Weber 1998-09-11 0:00 ` Fixed point design error in Ada95 Wayne Magor 1 sibling, 2 replies; 20+ messages in thread From: dewarr @ 1998-09-10 0:00 UTC (permalink / raw) In article <Ez28q4.FJL.0.-s@inmet.camb.inmet.com>, stt@houdini.camb.inmet.com (Tucker Taft) wrote: > Wayne Magor (wemagor@sym1.cca.rockwell.com_nospam) wrote: > > : I don't follow this newsgroup regularly, so I'm sorry if this topic has > : been discussed to death already. > > : I'd like to know if there is a plan to fix the design error in Ada95 that > : prevents user overloading of the "*" and "/" operators for fixed-point > : types (it results in an ambiguity on the call)? > > No solution has been defined. The best workaround is to use names > other than "*" and "/" for user-defined multiply and divide operations > for fixed-point types. You can overload the predefined "*" and "/" for > the type of interest with an "abstract" definition to make it less > likely they get misused. > > : ... The last I heard, the > : GNAT compiler did not implement fixed-point correctly (as per the Ada95 > : spec) so this wasn't a problem for that compiler. Is that true? Can > : other compilers do the same? > > This seems like the wrong solution. We did discuss various explicit > pragmas to get Ada-83 compatible behavior, but I don't believe > it went anywhere. > > : I had heard that this problem was known and was being discussed over a > : year ago. Was there a resolution, or is it being deferred to the next > : version of Ada? > > : Is there a web site that contains Ada language issues such as this? > > www.adaic.org has an archive of comments. If you have your own comments, > you can send them to ada9x-mrt@inmet.com, where they will get logged, and > redistributed to all interested parties once a day. The format for > comments is given in the Reference Manual. You can also get yourself > added to the "interested parties" list by sending mail to stt@inmet.com. > > : Also, what is the name of the Ada language maintenance committee? > > The Ada Rapporteur Group, which is part of ISO Working Group 9 (WG9) > > : Thanks, > : Wayne. > > -- > -Tucker Taft stt@inmet.com http://www.inmet.com/~stt/ > Intermetrics, Inc. Burlington, MA USA > An AverStar Company > The current version of GNAT Professional most certainly implements fixed-point in a manner consistent with the RM, and generates the very annoying ambiguities referred to here. (it is possible that various obsolete versions of GNAT may have done something else, but for the current version we do not know of any errors in this area). Note that if you use -gnat83, then of course the ambiguities are properly suppressed. Actually this is to be honest less annoying than you might think. Unless you are using fixed-point as "poor man's floating-point" [a dubious proposition now that virtually all processors do floating-point faster than fixed-point], it makes little sense to do something like function "*" (x,y : dollars_cents) return dollars_cents; since, as in this case, there is an obvious conceptual type error in this declaration. Robert Dewar Ada Core Technologies -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-10 0:00 ` dewarr @ 1998-09-10 0:00 ` Wayne Magor 1998-09-12 0:00 ` dewarr 1998-09-11 0:00 ` GNAT Professional ? Mats Weber 1 sibling, 1 reply; 20+ messages in thread From: Wayne Magor @ 1998-09-10 0:00 UTC (permalink / raw) dewarr@my-dejanews.com writes: >Actually this is to be honest less annoying than you might >think. Unless you are using fixed-point as "poor man's >floating-point" [a dubious proposition now that virtually >all processors do floating-point faster than fixed-point], >it makes little sense to do something like > > function "*" (x,y : dollars_cents) return dollars_cents; > >since, as in this case, there is an obvious conceptual >type error in this declaration. I'll certainly agree with you that there aren't a lot of uses for fixed-point operator overloading. We are running host-based simulations of avionics systems which run on a special avionics processor. That processor does not have floating point, but has something called fractional arithmetic. The fractional arithmetic does not work exactly the same way as Ada's fixed point. There is no overflow detection with this hardware, which is why the operator must be overloaded in order to properly simulate the way the software will operate in the target. The target compiler is an Ada83 compiler, but the host compiler is an Ada95 compiler. It is unfortunate that Ada95 is not 100% backward compatible in this area, even if it has little impact on the user community. A pragma to give Ada83 operation would be a good solution. Thanks, Wayne. ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-10 0:00 ` Wayne Magor @ 1998-09-12 0:00 ` dewarr 0 siblings, 0 replies; 20+ messages in thread From: dewarr @ 1998-09-12 0:00 UTC (permalink / raw) In article <6t9dlk$e0t1@onews.collins.rockwell.com>, > I'll certainly agree with you that there aren't a lot of uses for > fixed-point operator overloading. > > We are running host-based simulations of avionics systems which run > on a special avionics processor. That processor does not have > floating point, but has something called fractional arithmetic. > > The fractional arithmetic does not work exactly the same way as > Ada's fixed point. There is no overflow detection with this > hardware, which is why the operator must be overloaded in order > to properly simulate the way the software will operate in the > target. The target compiler is an Ada83 compiler, but the host > compiler is an Ada95 compiler. > > It is unfortunate that Ada95 is not 100% backward compatible in > this area, even if it has little impact on the user community. > > A pragma to give Ada83 operation would be a good solution. > > Thanks, > Wayne. First, a note, Ada does not require overflow detection for fixed-point, you seem from the above to think it does, so that is not a problem with your processor. The provision of the Machine_Overflows attribute is intended precisely to take care of this situation. Second, you obviously don't need operator overloading, there are perfectly reasonable work arounds here. They are a bit annoying, but certainly acceptable for new code. I agree that with legacy code you are in trouble, this is indeed one of the most severe incompatibilities between Ada 83 and Ada 95. I shouted around insisting that we should fix it when it was first noticed (which was rather late), but it seemed "too-late-at-this-stage" to do anything about it to most people, and perhaps they were right. -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* GNAT Professional ? 1998-09-10 0:00 ` dewarr 1998-09-10 0:00 ` Wayne Magor @ 1998-09-11 0:00 ` Mats Weber 1998-09-11 0:00 ` dewarr 1998-09-11 0:00 ` dennison 1 sibling, 2 replies; 20+ messages in thread From: Mats Weber @ 1998-09-11 0:00 UTC (permalink / raw) dewarr@my-dejanews.com wrote: > The current version of GNAT Professional most certainly [...] ^^^^^^^^^^^^ A new name ? When will we get Visual GNAT ? :-) ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-11 0:00 ` GNAT Professional ? Mats Weber @ 1998-09-11 0:00 ` dewarr 1998-09-12 0:00 ` Paul Whittington 1998-09-11 0:00 ` dennison 1 sibling, 1 reply; 20+ messages in thread From: dewarr @ 1998-09-11 0:00 UTC (permalink / raw) In article <35F91C48.87202332@elca-matrix.ch>, Mats.Weber@elca-matrix.ch wrote: > dewarr@my-dejanews.com wrote: > > > The current version of GNAT Professional most certainly [...] > ^^^^^^^^^^^^ > > A new name ? When will we get Visual GNAT ? :-) > We use the term GNAT Professional to distinguish this fully supported commercial product from the unsupported public version of GNAT. Robert Dewar Ada Core Technologies -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-11 0:00 ` dewarr @ 1998-09-12 0:00 ` Paul Whittington 1998-09-14 0:00 ` dewarr 1998-09-14 0:00 ` Al Christians 0 siblings, 2 replies; 20+ messages in thread From: Paul Whittington @ 1998-09-12 0:00 UTC (permalink / raw) What public version? In two days it'll be one year since the last "public" release of GNAT :( dewarr@my-dejanews.com wrote: > > In article <35F91C48.87202332@elca-matrix.ch>, > Mats.Weber@elca-matrix.ch wrote: > > dewarr@my-dejanews.com wrote: > > > > > The current version of GNAT Professional most certainly [...] > > ^^^^^^^^^^^^ > > > > A new name ? When will we get Visual GNAT ? :-) > > > > We use the term GNAT Professional to distinguish this fully > supported commercial product from the unsupported > public version of GNAT. > > Robert Dewar > Ada Core Technologies > > -----== Posted via Deja News, The Leader in Internet Discussion ==----- > http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum -- Paul Whittington GrepNet, Inc. paul@grep.net "Even if you're on the right track you'll get run over if you stand still." Will Rodgers ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-12 0:00 ` Paul Whittington @ 1998-09-14 0:00 ` dewarr 1998-09-15 0:00 ` Paul Whittington 1998-09-14 0:00 ` Al Christians 1 sibling, 1 reply; 20+ messages in thread From: dewarr @ 1998-09-14 0:00 UTC (permalink / raw) In article <35FABAEA.BBA81103@grep.net>, Paul Whittington <paul@grep.net> wrote: > What public version? > > In two days it'll be one year since the last "public" release of GNAT :( The current publicly released version of GNAT is 3.10p, which indeed was released about a year ago. Our general plan is to make new public releases on approximately a 12 month schedule. We are fairly close to on track for that. We expect to release GNAT Professional 3.11b in the next day or two (we will announce that release on CLA, with details). Assuming we have no packaging/installation problems in our final builds, which we will determine from customer feedback, then the corresponding 3.11p release will follow. We have had a 3.11b-beta out for a few weeks so we do not expect any major suprises. As always we like to be VERY sure that there are no installation glitches in the public release, since we know that a LOT of people will be trying to install it without support, and we want that to be as smooth as possible. We will make all support announcements on CLA at the appropriate point. Robert Dewar Ada Core Technologies -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-14 0:00 ` dewarr @ 1998-09-15 0:00 ` Paul Whittington 1998-09-15 0:00 ` Peter Hermann 1998-09-15 0:00 ` Markus Kuhn 0 siblings, 2 replies; 20+ messages in thread From: Paul Whittington @ 1998-09-15 0:00 UTC (permalink / raw) Thanks for the WONDERFUL news Robert :) I know that you're running a business at ACT and that the demands of doing so have made it necessary for you to abandon your former ~$1200 per seat per year supported product offering that made GNAT a reasonable alternative to Delphi, VC++ etc. for us. I'm not happy to hear that ACT's plans only include an annual public release of GNAT :( We are a small company, and don't need the kind of support ACT provides in its product offerings; and we can't afford it :( We considered using the public version of GNAT and relying on our own skills, as well as the support of the wonderfully helpful folks that use GNAT around the world, and came to the conclusion that, unlike the Linux folks for instance, there just wasn't enough bug-fix/enhancement activity going on with the public release of GNAT. It sounds like ACT's plans support our observation :( I guess you at ACT have surveyed the Open Source landscape and decided that unlike some of the other products in that space (e.g. GCC, Tcl/Tk) that provide source upgrades on a frequent basis doing so with GNAT is not in your best interest. Its your business, and you have to make the call. I do however have a request. I request that you read the following statements, and those of anyone else that cares to chime in, and reconsider your decision to release only once a year or so. Changing your policy and releasing more frequently would not damage your reputation as a supplier of high-quality supported Open Source software. I think that's already been established. On the contrary, it would serve to backup any commitment ACT has to the tradition of the Open Source community with concrete action consistent with such a commitment. Thus improving your standing as an Open Source supplier. Additionally, it would help to stimulate the development and use of Ada in commercial software projects, thus increasing ACT's potential "supported product" market. On that point, it's not the wealthy conservative corporate IT organizations, for the most part, that are going to be willing to take a chance, use Ada, and see if the Ada ROI is real. Rather its the small software developer, representing equally small and aggressive business clients that are always looking for an edge, that's going to be willing to find out if Ada development and maintenance is really 50% cheaper. If its true the small developer's clients will benefit greatly, larger IT organizations will get interested, and the small developer may become a larger developer who can afford ACT's supported product offerings :) In our case, we'd love to be developing state-of-the-art corporate MIS systems with integrated E-Commerce deployed on intranets, extranets, and the Internet using Ada's superior software engineering features, tasking and distributed system capabilities. The Ada community as a whole, and ACT specifically, could be benefiting from our work and success, as well as the work and success of others. Finally, I submit that making more frequent releases would be somewhat of an invitation to folks to get more involved in the development of GNAT itself, and tools to support the successful use of GNAT in a variety of domains. Now I know that there are already many groups and individuals involved in GNAT related development, and that more involvement could be as much of a problem for ACT as a benefit, but having played in the Delphi arena for some time now I do think that the Ada arena could stand some growth along these lines. I have the highest respect and admiration for ACT's GNAT team, and more eyes, experiences, and imaginations couldn't hurt. TTFN Paul dewarr@my-dejanews.com wrote: > > In article <35FABAEA.BBA81103@grep.net>, > Paul Whittington <paul@grep.net> wrote: > > What public version? > > > > In two days it'll be one year since the last "public" release of GNAT :( > > The current publicly released version of GNAT is 3.10p, which > indeed was released about a year ago. Our general plan is > to make new public releases on approximately a 12 month > schedule. > > We are fairly close to on track for that. We expect to > release GNAT Professional 3.11b in the next day or two (we > will announce that release on CLA, with details). > > Assuming we have no packaging/installation problems in our > final builds, which we will determine from customer feedback, > then the corresponding 3.11p release will follow. We have had > a 3.11b-beta out for a few weeks so we do not expect any > major suprises. As always we like to be VERY sure that there > are no installation glitches in the public release, since we > know that a LOT of people will be trying to install it without > support, and we want that to be as smooth as possible. > > We will make all support announcements on CLA at the > appropriate point. > > Robert Dewar > Ada Core Technologies > > -----== Posted via Deja News, The Leader in Internet Discussion ==----- > http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum -- Paul Whittington GrepNet, Inc. paul@grep.net "Even if you're on the right track you'll get run over if you stand still." Will Rodgers ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-15 0:00 ` Paul Whittington @ 1998-09-15 0:00 ` Peter Hermann 1998-09-15 0:00 ` dewarr 1998-09-15 0:00 ` Markus Kuhn 1 sibling, 1 reply; 20+ messages in thread From: Peter Hermann @ 1998-09-15 0:00 UTC (permalink / raw) Paul Whittington <paul@grep.net> wrote: [snip a lot] > We are a small company, and don't need the kind of support ACT provides > in its product offerings; and we can't afford it :( We considered ... > I request that you read the following statements, and those of anyone > else that cares to chime in, and reconsider your decision to release > only once a year or so. ... > Additionally, it would help to stimulate the development and use of > Ada in commercial software projects, thus increasing ACT's potential > "supported product" market. ... > take a chance, use Ada, and see if the Ada ROI is real. Rather its ... > ... The Ada community as a > whole, and ACT specifically, could be benefiting from our work and > success, as well as the work and success of others. ... > respect and admiration for ACT's GNAT team, and more eyes, experiences, > and imaginations couldn't hurt. Feedback is a precious good. ACT discourages this free income in-so-far that non-paying customers can't see the status of their contributions, like thrown into a black hole. So why reporting? -- Peter Hermann Tel+49-711-685-3611 Fax3758 ica2ph@csv.ica.uni-stuttgart.de Pfaffenwaldring 27 Raum 114, D-70569 Stuttgart Uni Computeranwendungen http://www.csv.ica.uni-stuttgart.de/homes/ph/ Team Ada: "C'mon people let the world begin" (Paul McCartney) ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-15 0:00 ` Peter Hermann @ 1998-09-15 0:00 ` dewarr 0 siblings, 0 replies; 20+ messages in thread From: dewarr @ 1998-09-15 0:00 UTC (permalink / raw) In article <6tlo7s$p4r$1@infosun2.rus.uni-stuttgart.de>, Peter Hermann <ica2ph@alpha1.csv.ica.uni-stuttgart.de> wrote: Feedback is a precious good. ACT discourages this free income > in-so-far that non-paying customers can't see the status of their > contributions, like thrown into a black hole. So why reporting? Well of course Peter is entitled to his opinion, and is free to make his own decisions, but just to state ACT policy here, we will receive bug reports from users of the public version if they are properly formatted and complete with sources, and they do not go into a black hole, but on the contrary do get examined sooner or later. Of course they do have rather low priority compared to problems and questions from our paying customers. Providing tracking information for such bugs is not only time consuming, but we have in the past had many experiences of people demanding that we hurry up and fix their bug even though they are not supported customers, in some cases people have got quite loud and angry. It is surprising what some people expect for free. Anyway, we don't have the resources to track reports from non-supported customers, so we are not able to provide this service. If you need this kind of tracking, you need to be a supported customer. But we certainly thank those users of the public version, who unlike Peter, find it worth while to take the effort to report problems, and in the rare cases where these are actually new bug reports, these problems do get fixed. Robert Dewar Ada Core Technologies -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-15 0:00 ` Paul Whittington 1998-09-15 0:00 ` Peter Hermann @ 1998-09-15 0:00 ` Markus Kuhn 1 sibling, 0 replies; 20+ messages in thread From: Markus Kuhn @ 1998-09-15 0:00 UTC (permalink / raw) Paul Whittington wrote: > I'm not happy to hear that ACT's plans only include an annual public > release of GNAT :( > > We considered > using the public version of GNAT and relying on our own skills, as well > as the support of the wonderfully helpful folks that use GNAT around > the world, and came to the conclusion that, unlike the Linux folks > for instance, there just wasn't enough bug-fix/enhancement activity > going on with the public release of GNAT. It sounds like ACT's plans > support our observation :( Actually, there are plans to set up a more Linux-like maintained version of GNAT. We were just waiting on the next public release to have an up-to-date starting point, because most of the more urgent problems seem to be already addressed in the expected 3.11p release. See http://www.cl.cam.ac.uk/~mgk25/linux-ada/ for more info and join the mailing list if you are interested to contribute. -- Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK email: mkuhn at acm.org, home page: <http://www.cl.cam.ac.uk/~mgk25/> ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-12 0:00 ` Paul Whittington 1998-09-14 0:00 ` dewarr @ 1998-09-14 0:00 ` Al Christians 1 sibling, 0 replies; 20+ messages in thread From: Al Christians @ 1998-09-14 0:00 UTC (permalink / raw) Paul Whittington wrote: > > What public version? > > In two days it'll be one year since the last "public" release of GNAT In some discussion of GPL, ACT, etc, last year, here's what Robert Dewar explained about this last year, according to deja news: -----------------------------------Excerpt follows -------------------- Note that people's willingness to abide by the informal ?do not distribute? rules is based on their perception that the request is reasonable, and is indeed based on a concern to avoid premature distribution. If they felt that the request was based on a desire to hoard software that was in fact ready for wide distribution, they would not concur, and the redistribution would occur. There is a huge philosophical difference between seeing distribution restricted because a group of people agree that it is not a good idea for the good of the project involved to distribute software prematurely, and a situation in which distributable software is being hoarded. ---------------------------End of Excerpt ----------------------- ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: GNAT Professional ? 1998-09-11 0:00 ` GNAT Professional ? Mats Weber 1998-09-11 0:00 ` dewarr @ 1998-09-11 0:00 ` dennison 1 sibling, 0 replies; 20+ messages in thread From: dennison @ 1998-09-11 0:00 UTC (permalink / raw) In article <35F91C48.87202332@elca-matrix.ch>, Mats.Weber@elca-matrix.ch wrote: > dewarr@my-dejanews.com wrote: > > > The current version of GNAT Professional most certainly [...] > ^^^^^^^^^^^^ > > A new name ? When will we get Visual GNAT ? :-) > I'm holding out for G++ :-) -- T.E.D. -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-10 0:00 ` Tucker Taft 1998-09-10 0:00 ` dewarr @ 1998-09-11 0:00 ` Wayne Magor 1998-09-11 0:00 ` dewarr 1 sibling, 1 reply; 20+ messages in thread From: Wayne Magor @ 1998-09-11 0:00 UTC (permalink / raw) (Tucker Taft) writes: >www.adaic.org has an archive of comments. If you have your own comments, >you can send them to ada9x-mrt@inmet.com, where they will get logged, and >redistributed to all interested parties once a day. Something is wrong with that website. I get a site that talks about registering domains at site.register.com. When I go to the site the web address changes to this: http://adaic.org/future.shtml Do you know why it is doing that? Is it still working for you? By the way, why did the pragma to give Ada83 operation for fixed point operators go nowhere? Not enough interest or was it a more philosophical reason? Were there strong objections to adding that pragma? Thanks, Wayne. ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-11 0:00 ` Fixed point design error in Ada95 Wayne Magor @ 1998-09-11 0:00 ` dewarr 1998-09-12 0:00 ` Robert I. Eachus 0 siblings, 1 reply; 20+ messages in thread From: dewarr @ 1998-09-11 0:00 UTC (permalink / raw) In article <6ta5h2$e0b2@onews.collins.rockwell.com>, No@Junk.Mail wrote: > > (Tucker Taft) writes: > > >www.adaic.org has an archive of comments. If you have your own comments, > >you can send them to ada9x-mrt@inmet.com, where they will get logged, and > >redistributed to all interested parties once a day. > > Something is wrong with that website. I get a site that talks about > registering domains at site.register.com. When I go to the site the > web address changes to this: > > http://adaic.org/future.shtml > > Do you know why it is doing that? Is it still working for you? > > By the way, why did the pragma to give Ada83 operation for fixed point > operators go nowhere? Not enough interest or was it a more philosophical > reason? Were there strong objections to adding that pragma? > > Thanks, > Wayne. > A pragma is obviously the wrong solution. It would be a nasty kludge at best. Pragmas are not supposed to affect the legality of programs. -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-11 0:00 ` dewarr @ 1998-09-12 0:00 ` Robert I. Eachus 1998-09-12 0:00 ` dewarr 0 siblings, 1 reply; 20+ messages in thread From: Robert I. Eachus @ 1998-09-12 0:00 UTC (permalink / raw) In article <6tb0j5$4rg$1@nnrp1.dejanews.com> dewarr@my-dejanews.com writes: > A pragma is obviously the wrong solution. It would be a nasty > kludge at best. Pragmas are not supposed to affect the legality > of programs. I agree. This is one of the cases that 3.5.6(8) is supposed to address. The interesting thing is that Wayne Magor seems to have identified a case of potentially general interest. What Wayne needs is a nonstandard fixed point type which corresponds to his hardware. But he could build that out of a nonstandard fixed type which just got rid of the special "*" and "/" operators. If someone wants to do this, be sure to take advantage of Reduced Accuracy Subtypes from J.3: subtype My_Fixed is Nonstandard.Fixed delta 0.125; -- Robert I. Eachus with Standard_Disclaimer; use Standard_Disclaimer; function Message (Text: in Clever_Ideas) return Better_Ideas is... ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-12 0:00 ` Robert I. Eachus @ 1998-09-12 0:00 ` dewarr 1998-09-17 0:00 ` Robert I. Eachus 0 siblings, 1 reply; 20+ messages in thread From: dewarr @ 1998-09-12 0:00 UTC (permalink / raw) In article <EACHUS.98Sep11203812@spectre.mitre.org>, eachus@spectre.mitre.org (Robert I. Eachus) wrote: > In article <6tb0j5$4rg$1@nnrp1.dejanews.com> dewarr@my-dejanews.com writes: > > > A pragma is obviously the wrong solution. It would be a nasty > > kludge at best. Pragmas are not supposed to affect the legality > > of programs. > > I agree. This is one of the cases that 3.5.6(8) is supposed to > address. The interesting thing is that Wayne Magor seems to have > identified a case of potentially general interest. What Wayne needs > is a nonstandard fixed point type which corresponds to his hardware. > But he could build that out of a nonstandard fixed type which just got > rid of the special "*" and "/" operators. > > If someone wants to do this, be sure to take advantage of Reduced > Accuracy Subtypes from J.3: > > subtype My_Fixed is Nonstandard.Fixed delta 0.125; > > -- > > Robert I. Eachus > > with Standard_Disclaimer; > use Standard_Disclaimer; > function Message (Text: in Clever_Ideas) return Better_Ideas is... > Well I would agree he has identified this case, but it is a very well known one that has been much discussed. It is one of the more serious incompatibilities, and worse than that it is a case in which Ada 83 is far superior to Ada 95, there simply is no good solution to this in Ada 95. I am not even sure Robert Eachus' solution of indtroducing a peculiar non-standard fixed-point type is allowable from an implementation point of view, but I am happy to leave that issue moot, since in any case such an approach does not help the user. We are considering adding a pragma in GNAT that will cause GNAT to implement the obvious solution which should have been put into the language in the first place, namely a preference rule that prefers a user defined operator to the implicit one (that is only useful in limited circumstances). I really don't see the argument against this preference rule, it only affects programs that are currently illegal in Ada 95, and legal in Ada 83, and gives the (desirable) Ada 83 semantics in this case. The pragma is interesting, it is sort of a language extension but actually no more than the Ada_83 switch (-gnat83 or pragma Ada_83) itself. It is after all just a subset of the effect of that switch, assuming that it does indeed handle this case (which is true in the latest version of GNAT). Robert Dewar Ada Core Technologies -----== Posted via Deja News, The Leader in Internet Discussion ==----- http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum ^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: Fixed point design error in Ada95 1998-09-12 0:00 ` dewarr @ 1998-09-17 0:00 ` Robert I. Eachus 0 siblings, 0 replies; 20+ messages in thread From: Robert I. Eachus @ 1998-09-17 0:00 UTC (permalink / raw) In article <6tejfi$7pm$1@nnrp1.dejanews.com> dewarr@my-dejanews.com writes: > Well I would agree he has identified this case, but it is > a very well known one that has been much discussed. It is > one of the more serious incompatibilities, and worse than > that it is a case in which Ada 83 is far superior to Ada > 95, there simply is no good solution to this in Ada 95. Sorry, the particular case of general interest that was identified was for a type which did not have ANY fixed*fixed or fixed/fixed operators. Yes, everyone has known about the overloading problem. But a type with no predefined multiply and divide operations (other than those for Integer) seems a lot easier to create. > I am not even sure Robert Eachus' solution of indtroducing > a peculiar non-standard fixed-point type is allowable from > an implementation point of view, but I am happy to leave > that issue moot, since in any case such an approach does > not help the user. Why not? RM 3.5.6(8) seems very clear: "An implementation may place arbitrary restrictions on the use of such types; it is implementation defined whether operators that are predefined for 'any real type' are defined for a a particular nonstandard real type." I guess you could argue that the operations to be disallowed are of type _universal_fixed_, but really we are talking about disallowing the implicit conversions to _universal_fixed_ for these nonstandard types. > We are considering adding a pragma in GNAT that will cause > GNAT to implement the obvious solution which should have been > put into the language in the first place, namely a preference > rule that prefers a user defined operator to the implicit > one (that is only useful in limited circumstances). Sounds reasonable. This is as you point out, purely a language extension. Actually, I personally think the right idea is to add such a rule to 8.6(29). This might be a good case for a non-binding AI, to be made binding if and when it is widely supported. -- Robert I. Eachus with Standard_Disclaimer; use Standard_Disclaimer; function Message (Text: in Clever_Ideas) return Better_Ideas is... ^ permalink raw reply [flat|nested] 20+ messages in thread
end of thread, other threads:[~1998-09-17 0:00 UTC | newest] Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 1998-09-09 0:00 Fixed point design error in Ada95 Wayne Magor 1998-09-10 0:00 ` Tucker Taft 1998-09-10 0:00 ` dewarr 1998-09-10 0:00 ` Wayne Magor 1998-09-12 0:00 ` dewarr 1998-09-11 0:00 ` GNAT Professional ? Mats Weber 1998-09-11 0:00 ` dewarr 1998-09-12 0:00 ` Paul Whittington 1998-09-14 0:00 ` dewarr 1998-09-15 0:00 ` Paul Whittington 1998-09-15 0:00 ` Peter Hermann 1998-09-15 0:00 ` dewarr 1998-09-15 0:00 ` Markus Kuhn 1998-09-14 0:00 ` Al Christians 1998-09-11 0:00 ` dennison 1998-09-11 0:00 ` Fixed point design error in Ada95 Wayne Magor 1998-09-11 0:00 ` dewarr 1998-09-12 0:00 ` Robert I. Eachus 1998-09-12 0:00 ` dewarr 1998-09-17 0:00 ` Robert I. Eachus
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