Record comparision ?

Record comparision ?

[Prateek S Fulzele]

Hi everybody!

Here I have some doubts regarding record comparisions done in ADA.

Read this code sample:

type REC_TYPE;
type REC_PTR_TYPE is access REC_TYPE;
type REC_TYPE is
     record
	INT1 : INTEGER;
        INT2 : INTEGER;
     end record;

-- now I declare two variables of REC_PTR_TYPE
REC_PTR1, REC_PTR2 : REC_PTR_TYPE;

-- then, assign some values to the record members of 
-- REC_PTR1, REC_PTR2.
....

-- now I say:
if REC_PTR1 < REC_PTR2 then
	-- do so and so ..
end if;

What is this signify ?
Does it mean that REC_PTR1.INT1 < REC_PTR2.INT1 or else ?

Please clarify.

Thanks in advance!

Prateek
-- 
-------------------------------------------------------------------
Prateek S Fulzele
Telecom Development Center,
Digital Equipment India Ltd, 
Bangalore
-------------------------------------------------------------------

Re: Record comparision ?

[Mark Fisher]

What your example actually does is compare the addresses of REC_PTR1
and REC_PTR2.

In order to compare the contents use

if REC_PTR1.all = REC_PTR2.all
then
.........

or refer to the components you wish to compare indiviudally.



Prateek S Fulzele <prateek@adca01.enet.dec.com> wrote in article
<3576214E.E7814E6B@adca01.enet.dec.com>...
> Hi everybody!
> 
> Here I have some doubts regarding record comparisions done in ADA.
> 
> Read this code sample:
> 
> type REC_TYPE;
> type REC_PTR_TYPE is access REC_TYPE;
> type REC_TYPE is
>      record
> 	INT1 : INTEGER;
>         INT2 : INTEGER;
>      end record;
> 
> -- now I declare two variables of REC_PTR_TYPE
> REC_PTR1, REC_PTR2 : REC_PTR_TYPE;
> 
> -- then, assign some values to the record members of 
> -- REC_PTR1, REC_PTR2.
> ....
> 
> -- now I say:
> if REC_PTR1 < REC_PTR2 then
> 	-- do so and so ..
> end if;
> 
> What is this signify ?
> Does it mean that REC_PTR1.INT1 < REC_PTR2.INT1 or else ?
> 
> Please clarify.
> 
> Thanks in advance!
> 
> Prateek
> -- 
> -------------------------------------------------------------------
> Prateek S Fulzele
> Telecom Development Center,
> Digital Equipment India Ltd, 
> Bangalore
> -------------------------------------------------------------------
> 

Re: Record comparision ?

[Niklas Holsti]

Prateek S Fulzele wrote:
> 
> Hi everybody!
> 
> Here I have some doubts regarding record comparisions done in ADA.
> 
> Read this code sample:
> 
> type REC_TYPE;
> type REC_PTR_TYPE is access REC_TYPE;
> type REC_TYPE is
>      record
>         INT1 : INTEGER;
>         INT2 : INTEGER;
>      end record;
> 
> -- now I declare two variables of REC_PTR_TYPE
> REC_PTR1, REC_PTR2 : REC_PTR_TYPE;
> 
> -- then, assign some values to the record members of
> -- REC_PTR1, REC_PTR2.
> ....
> 
> -- now I say:
> if REC_PTR1 < REC_PTR2 then
>         -- do so and so ..
> end if;
> 
> What is this signify ?

The ordering operators "<" etc. are not predefined for access types
such as REC_PTR_TYPE (nor for record types such as REC_TYPE),
therefore the above has no significance in Ada and any Ada compiler
should
reject it with an error message.

If you want to, you can define "<" for REC_PTR_TYPE or REC_TYPE to
have any meaning you like, by writing your own function with the profile

   function "<" (Left, Right: REC_PTR_TYPE)
   return boolean

or using REC_TYPE, respectively.

Re: Record comparision ?

[John English]

Prateek S Fulzele (prateek@adca01.enet.dec.com) wrote:
: type REC_TYPE;
: type REC_PTR_TYPE is access REC_TYPE;
: type REC_TYPE is
:      record
: 	INT1 : INTEGER;
:         INT2 : INTEGER;
:      end record;

: REC_PTR1, REC_PTR2 : REC_PTR_TYPE;

: if REC_PTR1 < REC_PTR2 then

This compares the access values (pointers). If you want to compare
the components, use Rec_Ptr1.Int1 < Rec_Ptr2.Int2, and if you want
to compare the complete records, use Rec_Ptr1.all < Rec_Ptr2.all
(but then you'll have to define your own "<" operator for Rec_Types,
as for Rec_Ptr_Type).

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