Re: Booch: iterator invalidation

[porton@ex-code.com (Victor Porton)]

In article <uptta4kgc.fsf@gsfc.nasa.gov>,
	Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov> writes:
> porton@ex-code.com (Victor Porton) writes:
> 
>> I'm not about asserting but about records which have or don't have
>> a component dependingly on whether it is the debuging version. 
> 
> Hmm. I've never done that for testing. Can you give a real example?
> What sort of "additional information" would you add?
> 
> I've used "debug storage pools" that report statistics on
> allocations/deallocations. I guess that is a form of what you are
> talking about here.

Yes, it is of such kind. Also it may be e.g. back references from
a container to iterators for checking validity etc.

>> Can variant records be used for this without lost of space
>> efficiency?
>>
>> type T_Internal(Debug: Boolean) is
>>   record
>>     -- ...
>>     case Debug is
>>       when True =>
>>         -- ... additional debugging stuff
>>       when others =>
>>         null;
>>     end case;
>>   end record;
>> 
>> type T is T_Internal(Use_Debug); -- Use_Debug is a Boolean _constant_
>> 
>> Will this not bring "additional debugging stuff" in the release
>> version (when Use_Debug=False)?
> 
> Now everything that uses T_Internal has to specify a Debug
> discriminant. To intrusive for my taste.

It is meant for user code to use _only_ T, not T_Internal.
(In OO style T_Internal should be in private section.)

All compiler implementors should consider this to ensure that
they have zero space-efficiency.