A question about v'range...?

A question about v'range...?

[eranshap]

Hi All,

I have the following program:

--BEGINNING OF PROGRAM

with Ada.Text_IO;
procedure taskmain is
  NUM_OF_ELEMENTS : constant Integer := 100;
  NUM_OF_TASKS : constant Integer := 10;
  
  type array_type is array (Integer range <>) of Positive;
  
  procedure Find_primes (vector : in array_type; num : in Positive) is
    
    task Manage;
    
    task body Manage is
      ind : Positive;
    begin
      for k in vector'range loop
        ind := k mod num; 
        Ada.Text_IO.Put_line (positive'image (k));
        Ada.Text_IO.Put_line (integer'image (vector'first));
        Ada.Text_IO.Put_line (integer'image (vector'last));
      end loop;
    end Manage;
    
  begin    -- of Procedure find_primes
    null;
  end Find_primes;
  
  vect : array_type(1..NUM_OF_ELEMENTS);
  
begin  -- of procedure taskmain
  for inc in vect'range loop
    vect(inc) := inc;
  end loop;
  Find_primes (vect, NUM_OF_TASKS);
end;

--END OF PROGRAM

And I get this output:

 1
 1
 100
 2
 1
 100
 3
 1
 100
 4
 1
 100
 5
 1
 100
 6
 1
 100
 7
 1
 100
 8
 1
 100
 9
 1
 100

This means that vector'range inside the task Manage is 1..9, while
vector'first is 1, and vector'last is 100, as printed.

I can also add, that when I did the same printing with the taskmain
procedure, it computed it correctly, i.e. vect'range is 1..100.

Why does this happen?

What can I do to correct it?

Re: A question about v'range...?

[Matthias Oltmanns]

The problem is not the vector'range inside the task. The loop will iterate
through 1 .. 100, but you get a CONSTRAINT ERROR after the 10. iteration.
Take a look at the line

  ind := k mod num; -- (num=10)

For k= 10, 20, ... the expression evaluates to zero, but the variable 'ind' is
of type Positive.
You should spend the variable 'ind' the type Natural and all work fine.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Matthias Oltmanns                    Daimler-Benz Aerospace
                                       Dornier
  - - - - - - - - - -                  Information and
  Tel: +49 7545 8 5683                 Communication Systems
  FAX: +49 7545 8 4504
  email: Oltmanns@vfmail.dofn.de
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Re: A question about v'range...?

[fd]

eranshap@netvision.net.il wrote:

: Hi All,

: I have the following program:

: --BEGINNING OF PROGRAM

: with Ada.Text_IO;
: procedure taskmain is
:   NUM_OF_ELEMENTS : constant Integer := 100;
:   NUM_OF_TASKS : constant Integer := 10;
:   
:   type array_type is array (Integer range <>) of Positive;
:   
:   procedure Find_primes (vector : in array_type; num : in Positive) is
:     
:   ......

: --END OF PROGRAM

: And I get this output:

:  1
:  1
:  100
:  2
:  1
:  100
:  3
:  1
:  100
:  4
:  1
: ............

: This means that vector'range inside the task Manage is 1..9, while
: vector'first is 1, and vector'last is 100, as printed.

: I can also add, that when I did the same printing with the taskmain
: procedure, it computed it correctly, i.e. vect'range is 1..100.

: Why does this happen?

: What can I do to correct it?

I think you've got a problem with your Ada developpment system, the code that has been generated looks false, this is not normal. There is no Ada Standard explanation.

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Re: A question about v'range...?

[Matthias Oltmanns]

Franck Duluc wrote:
> You are probably right, since such a behaviour make the task dead and
> the exception is not propagated. But how do you explain that he said
> that the output is correct when it takes place in the main procedure.

I think that the erroneous statement was omitted in the main procedure. But
that is only speculative, all that we can do is to ask Eran.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Matthias Oltmanns                    Daimler-Benz Aerospace
                                       Dornier
  - - - - - - - - - -                  Information and
  Tel: +49 7545 8 5683                 Communication Systems
  FAX: +49 7545 8 4504
  email: Oltmanns@vfmail.dofn.de
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~