C's static variable

C's static variable

[RL]

Does anyone know how in Ada to produce the equivalent of a static
variable in C?

Re: C's static variable

[Matthew Heaney]

In article <34109F10.52E2@communique.net>, RL <rladner@communique.net> wrote:

>Does anyone know how in Ada to produce the equivalent of a static
>variable in C?

Funny, this is probably the most frequently asked question about Ada.  

The answer is to declare the variable in a static scope, ie in a package
spec or body:

package P is

   A_Static_Variable : Integer;

end;

P is a library level declaration of a package.  It lives as long as the
application does, so any variables there are equivalent to C static
variables.

Check out the Ada FAQ at the Ada home page:

<http://www.adahome.com>

--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271

Re: C's static variable

[Tom Moran]

> Does anyone know how in Ada to produce the equivalent of a static
> variable in C?
1) Any variable declared in a package in Ada is analogous to a
'global'ly declared variable in C.  But in Ada it can be inside the
private part of the specification, or in the body of the package, in
which case it retains its value like a C global, but is invisible to
other packages, unlike C.
2) If you want something like declaring a static *inside* a C function,
but it makes no sense to have a separate package usable by anybody, then
you can make an internal package:
package body Whatever is
...
   package Special_Routine_With_A_Static is
     function F(...  ;
   private
     Static_Variable : integer_or_something := some_initial_value;
   end Special_Routine_With_A_Static;
   package body Special_Routine_With_A_Static is
     function F(...
        -- uses and modifies Static_Fariable (in a task-safe/unsafe way)
     end F;
   end Special_Routine_With_A_Static;
...  -- more of package Whatever, including calls 
     -- on Special_Routine_With_A_Static.F
     -- and perhaps a 'renames' of that to a better name
end Whatever;