Efficiency of code generated by Ada compilers
in [ADA]
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From: Dmitry A. Kazakov on 12 Aug 2010 04:36 On Thu, 12 Aug 2010 00:54:52 -0700, Charles H. Sampson wrote: > Simon Wright <simon(a)pushface.org> wrote: > >> csampson(a)inetworld.net (Charles H. Sampson) writes: >> >>> I then overloaded "+" and "-" for (Bearing, Turn_Angle) arguments >>> and Bearing return value. In those functions is where the mod 360 >>> occurred. (Actually, mod 360.0, as it were.) >> >> Depending on what is doing the turning, in our application that would >> in some cases have to be mod 720.0 ... > > I'm puzzled. Unless you're very careful, intermediate calculations > could result in a quasi-Bearing of more than 360 degrees but I'm pretty > sure most programmers on my project would have been surprised to see a > real bearing of 360 degrees or more. Maybe it was rhumbs? Just could not resist, sorry (:-)) -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de
From: Brian Drummond on 12 Aug 2010 07:04 On Thu, 12 Aug 2010 00:54:52 -0700, csampson(a)inetworld.net (Charles H. Sampson) wrote: >Simon Wright <simon(a)pushface.org> wrote: > >> csampson(a)inetworld.net (Charles H. Sampson) writes: >> >> > I then overloaded "+" and "-" for (Bearing, Turn_Angle) arguments >> > and Bearing return value. In those functions is where the mod 360 >> > occurred. (Actually, mod 360.0, as it were.) >> >> Depending on what is doing the turning, in our application that would >> in some cases have to be mod 720.0 ... > > I'm puzzled. Unless you're very careful, intermediate calculations >could result in a quasi-Bearing of more than 360 degrees but I'm pretty >sure most programmers on my project would have been surprised to see a >real bearing of 360 degrees or more. Some applications must distinguish between odd and even revolutions. Get it wrong and they might backfire. - Brian
From: Charles H. Sampson on 12 Aug 2010 13:10 Ludovic Brenta <ludovic(a)ludovic-brenta.org> wrote: > Charles H. Sampson wrote on comp.lang.ada: > [on defining "+" to add angles in modular arithmetic] > >> Sounds to me like a good way to do things. It would still be a good > >> idea if you called it "Turn_Left" or something like that, instead > >> of "+". But I don't object to "+". > > > > This was for the U. S. Navy, and "positive is right" is pretty much > > universal. For programmers, that is, not for sailors. They think port > > and starbord. > > Actually, to mathematicians and engineers, "+" is "turn counter- > clockwise" or "turn left", too. Granted, they'd probably use radians > instead of degrees. So, "+" meaning "turn right" is not as universal > as you might think. You're right, of course. I was being a bit too elliptical. I should have said Navy programmers (and Navy mathematicians, for that matter). In the U. S. Navy, a bearing of 0 degrees is due North, 90 degrees is East, etc. Charlie -- All the world's a stage, and most of us are desperately unrehearsed. Sean O'Casey
From: Jeffrey Carter on 12 Aug 2010 14:06 On 08/12/2010 10:10 AM, Charles H. Sampson wrote: > > You're right, of course. I was being a bit too elliptical. I > should have said Navy programmers (and Navy mathematicians, for that > matter). In the U. S. Navy, a bearing of 0 degrees is due North, 90 > degrees is East, etc. This is also the convention used in aviation. -- Jeff Carter "What I wouldn't give for a large sock with horse manure in it." Annie Hall 42 --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Simon Wright on 12 Aug 2010 15:23
csampson(a)inetworld.net (Charles H. Sampson) writes: > Simon Wright <simon(a)pushface.org> wrote: > >> csampson(a)inetworld.net (Charles H. Sampson) writes: >> >> > I then overloaded "+" and "-" for (Bearing, Turn_Angle) arguments >> > and Bearing return value. In those functions is where the mod 360 >> > occurred. (Actually, mod 360.0, as it were.) >> >> Depending on what is doing the turning, in our application that would >> in some cases have to be mod 720.0 ... > > I'm puzzled. Unless you're very careful, intermediate calculations > could result in a quasi-Bearing of more than 360 degrees but I'm pretty > sure most programmers on my project would have been surprised to see a > real bearing of 360 degrees or more. A tracker radar like this one (hope the link will work) might be able to turn through an unlimited number of revolutions, or (with a more mechanical design) there might be a limit on how many revs it could manage. So if it's currently pointing 10 degrees to starboard, how much further can it go before having to unwind? I agree that this is Training, not Bearing, of course. http://www.artisan3d.co.uk/static/bae_cimg_radar_Fi_latestReleased_bae_cimg_radar_Fi_Web.jpg |