Re: Printing the address

Re: Printing the address

[Maxim Reznik]

Actually, you don't need the address image to find if it is null. You can print instead

Put_Line (Boolean'Image (Boxes (n) = null));

When you really need the address image you can use

function System.Address_Image (A : Address) return String;

and an instantiation of

System.Address_To_Access_Conversions

generic package to convert Box_Acces value to System.Address.

PS. BTW, I would use a debugger in such cases.

Re: Printing the address

[Niklas Holsti]

On 2021-05-11 15:35, Maxim Reznik wrote:

> When you really need the address image you can use
> 
> function System.Address_Image (A : Address) return String;


That seems not to be a standard function, at least I can't find it in 
Ada RM 2012 or RM (draft) 202X. Probably a GNAT-specific addition to 
package System.

Re: Printing the address

[Niklas Holsti]

On 2021-05-11 13:38, ldries46 wrote:
> I Get an contstraint error in the line:
> /if Boxes(n).Status = manual or Boxes(n).Status = auto then/


That is either becase "n" is not in Boxes'Range, or because Boxes(n) is 
null. From the rest of your message, it seems you believe that the 
latter is the cause.

(Btw, a briefer expression is

    if Boxes(n).Status in manual | auto then ...

assuming that Box_Status is a discrete type.)


> where/:
>     Boxes     : Ar_Box;
>     type Box is record
>        Status  : Box_Status;
>        Nrs_pos : Ar_Pos;
>        x_val   : integer;
>        y_val   : integer;
>        Fill    : integer;
>     end record;
> ///   type Box_Acces is access all Box;
> /   type Ar_Box is array (1 .. Max_Num) of Box_Acces;
> 
> /To debug the program I need to finf where the constraint is
> possible a 0x0 somewhere in Box


I assume you mean that some element of Boxes is a null access. That may 
or may not be represented as 16#0#.


> How can I priint this value I tried converting it to and integer but I 
> couldn'd get that working


You don't have to print the value. All that should matter to you is 
whether the value is null or not, so:

    Put (if Boxes(n) = null then "null" else "not null");

(If you really want to print the address, do

    System.Storage_Elements.Integer_Address'Image (
       System.Storage_Elements.To_Integer (Boxes(n).all'Address))

but be sure to check for a null value of Boxes(n) first.)