null array constant in Ada 83

null array constant in Ada 83

[Martin Krischik]

Hi,

maintaining old code is such a great fun. Anybody know what goes where
the 4 dots are (an appropriate N_Sel_List_Entry is declared).

   subtype T_Sel_Entries is Integer range 0 ..
Selection_Types.Max_Selection_Results;

   type T_Sel_List is array (T_Sel_Entries range <>) of T_Sel_List_Entry;

   N_Sel_List : constant T_Sel_List (1 .. 0) := ....;

Or is it just plain impossible in Ada 83.

Regards

Martin
-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com

Re: null array constant in Ada 83

[Peter Hermann]

(others => ...

Re: null array constant in Ada 83

[Frank J. Lhota]

Martin Krischik wrote:
> Hi,
> 
> maintaining old code is such a great fun. Anybody know what goes where
> the 4 dots are (an appropriate N_Sel_List_Entry is declared).
> 
>    subtype T_Sel_Entries is Integer range 0 ..
> Selection_Types.Max_Selection_Results;
> 
>    type T_Sel_List is array (T_Sel_Entries range <>) of T_Sel_List_Entry;
> 
>    N_Sel_List : constant T_Sel_List (1 .. 0) := ....;
> 
> Or is it just plain impossible in Ada 83.
> 
> Regards
> 
> Martin

If N_Sel_Entry_Value is a value of type N_Sel_List_Entry, then you could 
write

    N_Sel_List : constant T_Sel_List (1 .. 0) :=
       (1 .. 0 => N_Sel_Entry_Value);

The fact that you have to provide a component value that is never used 
is a well known annoyance.
-- 
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Let everything be as it should be;
Thus shall it be!"
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Re: null array constant in Ada 83

[AdaMagica]

  N_Sel_List: constant T_Sel_List (1 .. 0) := (others => some_value);

should be OK (some_value will not be evaluated since the range is
empty).

Re: null array constant in Ada 83

[Martin Krischik]

Frank J. Lhota schrieb:
> Martin Krischik wrote:
>> Hi,
>>
>> maintaining old code is such a great fun. Anybody know what goes where
>> the 4 dots are (an appropriate N_Sel_List_Entry is declared).
>>
>>    subtype T_Sel_Entries is Integer range 0 ..
>> Selection_Types.Max_Selection_Results;
>>
>>    type T_Sel_List is array (T_Sel_Entries range <>) of T_Sel_List_Entry;
>>
>>    N_Sel_List : constant T_Sel_List (1 .. 0) := ....;
>>
>> Or is it just plain impossible in Ada 83.
>>
>> Regards
>>
>> Martin
> 
> If N_Sel_Entry_Value is a value of type N_Sel_List_Entry, then you could
> write
> 
>    N_Sel_List : constant T_Sel_List (1 .. 0) :=
>       (1 .. 0 => N_Sel_Entry_Value);

I see - I tried "other =>" - and that did not work at least not with Ada 83.

> The fact that you have to provide a component value that is never used
> is a well known annoyance.

I know. Even more interesting is creating a constant of a null record
(tied that in a prototype just recently). I found the syntax in the Ada
95 RM only to find out that Ada 83 does not know about it. But since it
was a prototype I did not bother looking into it.

Martin

-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com

Re: null array constant in Ada 83

[Jean-Pierre Rosen]

Martin Krischik a écrit :
>>    N_Sel_List : constant T_Sel_List (1 .. 0) :=
>>       (1 .. 0 => N_Sel_Entry_Value);
> 
> I see - I tried "other =>" - and that did not work at least not with Ada 83.
> 
True. The contexts where others => is allowed were extended in Ada 95,
and this is one of them.

-- 
---------------------------------------------------------
           J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr

Re: null array constant in Ada 83

[anon]

Even though there are many features that are the same, there are 
also many changes from Ada 83 to Ada 95 or Ada 2005 so that you 
should download and use the Ada 83 LRM for maintain Ada 83 programs.


So you might need to use "'First" or "'Last" to define a initial value 

   -- N_Sel_Entry_Value is used set to an inital value 

   N_Sel_Entry_Value : constant T_Sel_List_Entry := T_Sel_List_Entry'First;  

   N_Sel_List : constant T_Sel_List (1 .. 0) := (1 .. 0 => N_Sel_Entry_Value);



Ada 83 RM 3.2.1

    OPTION      : BIT_VECTOR(1 .. 10) := (others => TRUE); 

Then Ada 83 RM 3.6 defines
    type TABLE    is array(1 .. 10) of INTEGER;

then from, Ada 83 RM 4.3.2  Array Aggregates

    TABLE'(5, 8, 4, 1, others => 0)  --  see 3.6 





In <4a40c4e8$1@news.post.ch>, Martin Krischik <krischik@users.sourceforge.net> writes:
>Frank J. Lhota schrieb:
>> Martin Krischik wrote:
>>> Hi,
>>>
>>> maintaining old code is such a great fun. Anybody know what goes where
>>> the 4 dots are (an appropriate N_Sel_List_Entry is declared).
>>>
>>>    subtype T_Sel_Entries is Integer range 0 ..
>>> Selection_Types.Max_Selection_Results;
>>>
>>>    type T_Sel_List is array (T_Sel_Entries range <>) of T_Sel_List_Entry;
>>>
>>>    N_Sel_List : constant T_Sel_List (1 .. 0) := ....;
>>>
>>> Or is it just plain impossible in Ada 83.
>>>
>>> Regards
>>>
>>> Martin
>> 
>> If N_Sel_Entry_Value is a value of type N_Sel_List_Entry, then you could
>> write
>> 
>>    N_Sel_List : constant T_Sel_List (1 .. 0) :=
>>       (1 .. 0 => N_Sel_Entry_Value);
>
>I see - I tried "other =>" - and that did not work at least not with Ada 83.
>
>> The fact that you have to provide a component value that is never used
>> is a well known annoyance.
>
>I know. Even more interesting is creating a constant of a null record
>(tied that in a prototype just recently). I found the syntax in the Ada
>95 RM only to find out that Ada 83 does not know about it. But since it
>was a prototype I did not bother looking into it.
>
>Martin
>
>-- 
>mailto://krischik@users.sourceforge.net
>Ada programming at: http://ada.krischik.com