Re: Are global or persistent variables in ADA?

[Alan E & Carmel J Brain <aebrain@dynamite.com.au>]

Brian Franklin wrote:
> 
>   I haven't found this in any of my books on ADA. Can I have a
> procedure retain it's variable value after it returns to it's calling
> routine? In C  I can use STATIC in declaring such a variable.

Not quite, but you have a better alternative:

package SMALL_DATABASE is

  AnInteger : Integer;

end SMALL_DATABASE;


anything that with's SMALL_DATABASE is able to do anything at all with
the variable AnInteger. Read it, write to it, whatever. It's static, and
won't go away.


But... this is not always a good idea. Maybe you should have

package SMALL_DATABASE is

  function ReadInteger return Integer;

  procedure WriteInteger(Item : in Integer);

end SMALL_DATABASE;

and an appropriate body.

Maybe, and this is safer still, you should have a guardian task, so
calls are stackable, and the thing is re-usable in a multi-threaded
environment.


But often, the first version is enough. Only those packages that need to
look at/manipulate the data "with" it.

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