Re: += in ada

["Robert I. Eachus" <rieachus@comcast.net>]

Russ wrote:

> Oh, I see. So efficiency is no longer an issue. Well, excuse me, but I
> think we'd be better off leaving that judgment to each application
> developer. Controlling a building temperature is one thing, but
> delivering a cruise missile to Saddam Hussein's front door is quite
> another.

No.  Efficiency on the level you are talking about, in Ada, is something 
we delegate to the compiler.  We want software engineers, safety 
engineers, and security experts to be able to worry about much trickier 
stuff.  Do you want your security experts searching code for potential 
buffer overruns, or looking for covert timing channels?  In Ada, we 
prefer to leave the stuff that machines can do best to machines.

> Do you have any idea whatsoever how much computation is potentially
> involved in computing optimal conflict-free trajectories for thousands
> of airplanes? Here's a suggestion: if you don't know WTF you are
> talking about, STFU.

If you would like to get serious on this subject, ask me about an Ada 
implementation of the assignment problem that used sparse matrices, and 
a very fast algorithm.  (The air traffic control problem is just a huge 
assignment problem.  You want to assign aircraft to airspace most 
efficiently, subject to the very important constraint that there is at 
most one airplane in any available airspace. ;-)  As for whether or not 
that work is applicable to air traffic control, it was done as part of 
the RSIP upgrade of AWACS.  A major potential problem was that 
increasing the radar sensitivity would be useless without the ability to 
effectively track and manage all that traffic.

That is the level at which you should be worrying about efficiency, not 
the micro efficency of allocating temporaries.  And besides, as I said, 
in modern CPUs, anything you learned about that in school is totally 
obsolete.  That probably includes all classes in Assembler being taught 
right now.

-- 
                                                     Robert I. Eachus

"Quality is the Buddha. Quality is scientific reality. Quality is the 
goal of Art. It remains to work these concepts into a practical, 
down-to-earth context, and for this there is nothing more practical or 
down-to-earth than what I have been talking about all along...the repair 
of an old motorcycle."  -- from Zen and the Art of Motorcycle 
Maintenance by Robert Pirsig