Re: Puzzled by SPARK global aspect

[Anh Vo <anhvofrcaus@gmail.com>]

On Saturday, July 1, 2017 at 5:45:28 PM UTC-7, Anh Vo wrote:
> On Saturday, July 1, 2017 at 11:25:20 AM UTC-7, digitig wrote:
> > On Saturday, July 1, 2017 at 4:51:22 PM UTC+1, Anh Vo wrote:
> > > On Friday, June 30, 2017 at 2:29:38 PM UTC-7, digitig wrote:
> > Here's a fairly minimal spec and body, then, which gives the problem I describe:
> > 
> > ---- main.ads ----
> > package Main
> > with
> > SPARK_Mode => On
> >   is
> > type Quadrant_Specification is record
> >    N_Klingons: Integer := 0;
> > end record;
> > 
> > subtype Klingon_Counter is Integer range 0..20;
> > 
> >    type Quadrant_Specification_Array is
> >      array(1..8, 1..8)
> >      of Quadrant_Specification;
> > 
> > 
> >    function N_Total_Klingons return Integer
> >      with
> >        Global => null,
> >        Depends => (N_Total_Klingons'Result => null),
> >      Pre => True;
> > 
> > end Main;
> > 
> > ---- Main.adb ----
> > package body Main
> > with
> >   SPARK_Mode => On
> > is
> >    Quadrant_Specifications: Quadrant_Specification_Array;
> > 
> >    function N_Total_Klingons return Integer
> > --           with
> > --             Refined_Global => Quadrant_Specifications
> >    is
> >       Total: Integer := 0;
> >    begin
> >       for X in Quadrant_Specifications'Range loop
> >          for Y in Quadrant_Specifications'Range(2) loop
> >             Total := Total + Quadrant_Specifications(X, Y).N_Klingons;
> >          end loop;
> >       end loop;
> >       return Total;
> >    end N_Total_Klingons;
> > end Main;
> 
> Both Global and Depends are under umbrella of Abstract_State at the package level. Therefore, Abstract_State must be defined below. Note that Package_State is an arbitrary name.

package Main 
  with 
    SPARK_Mode => On, Abstract_State => Package_State
is 
--...

   function N_Total_Klingons return Integer 
     with 
       Global => Package_State,
       Depends => (N_Total_Klingons'Result => Package_State);

end Main;

In the package body, the Refined_State must be defined to associated with the constituents Quadrant_Specifications as shown below.

 
> package body Main 
>   with 
>     SPARK_Mode => On,
>     Refined_State => (Package_State => Quadrant_Specifications)
> is 
> -- ...
> 
> In addition, Global and Depends are defined below because this function depends on local global variable.
> 
>    function N_Total_Klingons return Integer 
>      with 
>        Global => Package_State,
>        Depends => (N_Total_Klingons'Result => Package_State)
>    is
>    -- ...
> 
> In the package body Refined_State must be defined to use Quadrant_Specifications as shown below.
> 
> package body Main 
>   with 
>     SPARK_Mode => On,
>     Refined_State => (Package_State => Quadrant_Specifications)
> is 
> -- ...
> 
> Moreover, Refined_Global and Refined_Depends aspects must be declared to use the array variable Quadrant_Specifications.


Sorry, I cut out some good part before hitting the send button. Please ignore the previously incomplete post. Below is the complete one.

Both Global and Depends are under umbrella of Abstract_State at the package level. Therefore, Abstract_State must be defined below. Note that Package_State is an arbitrary name.

package Main 
  with 
    SPARK_Mode => On, Abstract_State => Package_State
is 
--...

   function N_Total_Klingons return Integer 
     with 
       Global => Package_State,
       Depends => (N_Total_Klingons'Result => Package_State);

end Main;

In the package body, the Refined_State must be defined to associated with the constituents Quadrant_Specifications as shown below.

package body Main 
   with 
     SPARK_Mode => On,
     Refined_State => (Package_State => Quadrant_Specifications)
is 
 -- ...
 
In addition, Global and Depends are defined below because this function depends on local global variable.
 
    function N_Total_Klingons return Integer 
      with 
        Global => Package_State,
        Depends => (N_Total_Klingons'Result => Package_State)
    is
    -- ...