Re: Joint Strike Fighter

[Kilgallen@SpamCop.net (Larry Kilgallen)]

In article <3BEA9CED.8C6BF839@reges.org>, Rex Reges <Dogbert.EggsAndSpamWithoutTheSpam@reges.org> writes:

> Larry Kilgallen wrote:
>> 
>> In article <3BE853FD.513040F@reges.org>, Rex Reges <Dogbert.EggsAndSpamWithoutTheSpam@reges.org> writes:
>> 
>> > Upon this conclusion, I can now make sense of the Ada coding
>> > practices I've seen:
>> 
>> >  - Assigning all of the components of a record one at
>> >    a time instead of using an aggregate assignment.
>> 
>> It must be done separately if your design involves making
>> two successive assignments to the same component and none
>> to some other component.

> Generally, it is a good idea to make an aggregate assignment
> for a record, since any change in the record type will then
> cause a compiler error if some part of the code is not
> updated. I'm sure you are not suggesting that we eliminate
> this guideline, but rather allow exceptions.  I've ran into

Actually I was not even exceptions.  I merely made another
(failed) attempt at an implicit ":-)".  When will I learn :-)

> this guideline, but rather allow exceptions.  I've ran into
> a few myself:
> 
>   - Some structures are too big to even initialize with an
>     aggregate assignment (a 128kB memory mapped device control 
>     areas, for example).

That seems like a compiler limitation, which ultimately
should be corrected.

>   - When frequently appending to the same variable structure  
>     by  modifying the variant part is inefficient; it's better 
>     to expand the variable to the max expected size once, 
>     filling it with dummy data, and then overwrite the 
>     individual subcomponents one at a time.

There must be a way compilers could do that better.  Granted I
generally don't do speed-critical work, but I prefer something
that is more foolproof even if slightly slower.

>   - If there is the possibility that a subcomponent is 
>     out of range, then you need individual assignments of
>     the subcomponents to perform a constraint check. The 
>     constraint check is only required for the assignment 
>     operator and the constraint checks for a record assignment 
>     are only to verify the variant parts are in range. I've 

I would have guessed creation of the record aggregate would
have done constraint checking.  I gather my guess would
have been wrong.