Re: [SPARK] Code safety and information hiding

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

Jeffrey R. Carter wrote:

> As you're probably aware, rules with "always" in them always have 
> exceptions (including this rule). I have a rule that says always avoid 
> global variables. I'll accept a small number of well documented global 
> variables sometimes if the alternative is worse.

It's interesting to see this discussion, especially after the posts 
revealing that it's not really clear what "global" means.

Let's say I have a program composed of some subroutines or packages. 
Each subroutine has some local variables and each package has some state 
  and together they all cooperate according to what the whole is 
supposed to do.
Then I decide to break the system into separate processes, and for the 
sake of discussion what was a subroutine (or a package) originally 
becomes a separate process, all communicating using some form of IPC and 
still cooperating to achieve the supposed goals.

The point is that while chopping the system into pieces, what was local 
(or state) variable originally became global in the resulting smaller 
program.

Now - did I break SW principles and should I go to hell for making N 
programs with M global variables in each?
After all, if I draw the whole on the whiteboard, the diagram is the 
same as it was at the beginning, with boxes encapsulating state and 
arrows depicting the only possible interactions. So? :-)


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