Re: [SPARK] Code safety and information hiding

[Maciej Sobczak <no.spam@no.spam.com>]

Bj�rn Persson wrote:

>>> Now each main subprogram that was a subprogram (Ada doesn't have 
>>> subroutines) in the original has its own local variables.
>>
>> Which are global relatively to the process, and local relatively to the
>> distributed system as a whole.
> 
> No. They're declared inside the main subprogram and not visible to any 
> library-level packages, so they aren't truly global.

This is just hiding from discussion. :-)

If you rigorously stick to some chosen definition, then you can argue 
that such variables are not global.
But I will argue that a variable which is visible everywhere in the 
program (in the sense that every executable piece of code can access 
this variable) is effectively global in that program - it's the 
visibility in any given scope the makes something global or local, all 
the rest is only syntax.
Criticising the use of global variables without considering the full 
context of the given system is somewhat orthodox, even more so if only 
syntax is considered to be a distinguishing factor. I can imagine a 
program that uses global variables where "encapsulating" them into 
separate package(s) would only add clutter, without any real benefit.


-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/