Re: put of access type

[Rob Solomon <usenet@drrob1-noreply.com>]

>> I would like to output a pointer to the screen.  (I am just learning
>> Ada).  
>> 
>> How do I put(Any_Access_Type)
>
>You probably meant the address of the pointed object. Here you go. Let Ptr
>be a pointer to some object
>
>(with System.Storage_Elements;  use System.Storage_Elements;)
>
>   Integer_Address'Image (To_Integer (Ptr.all'Address)));
>
>Ptr.all'Address is the address of the object. To_Integer converts the
>address to a plain integer type (Integer_Address defined in
>System.Storage_Elements). This type can be output as any other.

I am trying to understand this.  

Back when I learned Modula-2, I learned that pointer types are
assignment compatible with System.Address and I understand them as
being the same thing.  They  differ in context, not value.

I see that access types are being used the same as pointer types, but
if I understand correctly, are actually quite different.  But I don't
understand how.  ie, how are access types and pointers different?

What is the difference between integer_address and address?

I need help with this code:

procedure adr is

c: integer;
x: aliased integer;
p1, p2 : access integer;
str : string (1..255);

Begin
  p1 := x'access;
  p2 := p1;
  str := integer_address'image(to_integer(p1.all'address));
  c := integer(to_integer(p2.all'address));

some put statements
end adr;

This compiles w/ GNAT under Ubuntu 9.04, but I am getting
constraint_error, range check failed.

I don't understand why