Puzzled by SPARK global aspect

Puzzled by SPARK global aspect

[digitig]

Suppose in my package specification I have

   type Quadrant_Specification_Array is 
   array(Global.Quadrant_X_Index'Range, Global.Quadrant_Y_Index'Range) 
   of Quadrant_Specification;

(With QuadrantSpecification being a record type) and in my package body I have:

   function N_Total_Klingons return Global.Klingon_Counter
       with
         Refined_Global => (Input => Quadrant_Specifications)
   is
      Total: Global.Klingon_Counter := 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;

Spark gives me an error
  useless refinement, subprogram "N_Total_Klingons" does not depend on abstract state with visible refinement

But if I take the Refined_Global specification out I get the error

  "Quadrant_Specifications" must be listed in the Global aspect of "N_Total_Klingons"

I feel I'm losing either way - if I do specify it I'm wrong, if I don't specify it I'm wrong.

How *do* I fix this?

Re: Puzzled by SPARK global aspect

[Anh Vo]

On Friday, June 30, 2017 at 2:29:38 PM UTC-7, digitig wrote:
> Suppose in my package specification I have
> 
>    type Quadrant_Specification_Array is 
>    array(Global.Quadrant_X_Index'Range, Global.Quadrant_Y_Index'Range) 
>    of Quadrant_Specification;
> 
> (With QuadrantSpecification being a record type) and in my package body I have:
> 
>    function N_Total_Klingons return Global.Klingon_Counter
>        with
>          Refined_Global => (Input => Quadrant_Specifications)
>    is
>       Total: Global.Klingon_Counter := 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;
> 
> Spark gives me an error
>   useless refinement, subprogram "N_Total_Klingons" does not depend on abstract state with visible refinement
> 
> But if I take the Refined_Global specification out I get the error
> 
>   "Quadrant_Specifications" must be listed in the Global aspect of "N_Total_Klingons"
> 
> I feel I'm losing either way - if I do specify it I'm wrong, if I don't specify it I'm wrong.
> 
> How *do* I fix this?

It is pretty hard to suggest advice since it is not a complete minimal code. In addition, I rather see the code instead of guessing. I would say your codes involve package Abstract State aspect.

Anh Vo

Re: Puzzled by SPARK global aspect

[digitig]

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:
> > Suppose in my package specification I have
> > 
> >    type Quadrant_Specification_Array is 
> >    array(Global.Quadrant_X_Index'Range, Global.Quadrant_Y_Index'Range) 
> >    of Quadrant_Specification;
> > 
> > (With QuadrantSpecification being a record type) and in my package body I have:
> > 
> >    function N_Total_Klingons return Global.Klingon_Counter
> >        with
> >          Refined_Global => (Input => Quadrant_Specifications)
> >    is
> >       Total: Global.Klingon_Counter := 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;
> > 
> > Spark gives me an error
> >   useless refinement, subprogram "N_Total_Klingons" does not depend on abstract state with visible refinement
> > 
> > But if I take the Refined_Global specification out I get the error
> > 
> >   "Quadrant_Specifications" must be listed in the Global aspect of "N_Total_Klingons"
> > 
> > I feel I'm losing either way - if I do specify it I'm wrong, if I don't specify it I'm wrong.
> > 
> > How *do* I fix this?
> 
> It is pretty hard to suggest advice since it is not a complete minimal code. In addition, I rather see the code instead of guessing. I would say your codes involve package Abstract State aspect.
> 
> Anh Vo

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;

Re: Puzzled by SPARK global aspect

[Anh Vo]

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 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.

Re: Puzzled by SPARK global aspect

[Anh Vo]

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
    -- ...