Alright, now for an Ada '95 question.

Alright, now for an Ada '95 question.

[Tom Di Sessa]

First of all, I want to thank the people who responded to my first(and
rather unpolite) post.  Thank you.

In Java, I am able to do this comparison:
(target is of Class(Type) Component, and Class Button is is derived from
Component)

if (target instanceof Button) {...}

Now, is there a way to do this comparison in Ada '95, if target was of
type Component'Class and Button was a derived type from Component?

-tom :)

-- 


+------------------------------------------------------------------+
| Thomas G. Di Sessa           ||                                  |
|   WPL Laboratories, Inc.     || Email: tdisessa@wpllabs.com      |
|   Whitehall Offices, Suite 6 || Voice: 610.658.2362 ext. 227     |
|   410 Lancaster Avenue       ||   Fax: 610.658.2361              |
|   Haverford, PA  19041       ||                                  |
+------------------------------------------------------------------+

Re: Alright, now for an Ada '95 question.

[Mike Bishop]

Tom Di Sessa wrote:
> 
> First of all, I want to thank the people who responded to my first(and
> rather unpolite) post.  Thank you.
> 
> In Java, I am able to do this comparison:
> (target is of Class(Type) Component, and Class Button is is derived from
> Component)
> 
> if (target instanceof Button) {...}
> 
> Now, is there a way to do this comparison in Ada '95, if target was of
> type Component'Class and Button was a derived type from Component?

The following comparisons can be done in Ada 95:

if target in Button then ...
if target in Component'class then ...

I don't know of a way to compare the types Button and Component in order
to determine if Button is derived from Component. That doesn't mean that
there is no way to do it, only that I don't know how to do it.

-- 
Mike Bishop         
mbishop@ghgcorp.com 
http://www.ghgcorp.com/mbishop/

Re: Alright, now for an Ada '95 question.

[Mark A Biggar]

In article <3213D46A.2404@ghgcorp.com> Mike Bishop <mbishop@ghgcorp.com> writes:
>Tom Di Sessa wrote:
>> First of all, I want to thank the people who responded to my first(and
>> rather unpolite) post.  Thank you.
>> In Java, I am able to do this comparison:
>> (target is of Class(Type) Component, and Class Button is is derived from
>> Component)
>> if (target instanceof Button) {...}
>> Now, is there a way to do this comparison in Ada '95, if target was of
>> type Component'Class and Button was a derived type from Component?
>The following comparisons can be done in Ada 95:
>if target in Button then ...
>if target in Component'class then ...
>I don't know of a way to compare the types Button and Component in order
>to determine if Button is derived from Component. That doesn't mean that
>there is no way to do it, only that I don't know how to do it.

The only way I can think of is to create a dummy object and use that:

declare
	target: Button;
begin
	if target in Component'Class then
		-- Button is derived from or subtype of Component
	end if;
end;

--
Mark Biggar
mab@wdl.lmco.com

Re: Alright, now for an Ada '95 question.

[Jon S Anthony]

In article <3213D46A.2404@ghgcorp.com> Mike Bishop <mbishop@ghgcorp.com> writes:

> I don't know of a way to compare the types Button and Component in
> order to determine if Button is derived from Component. That doesn't
> mean that there is no way to do it, only that I don't know how to do
> it.

I don't think you can do this directly as 4.4(8) rules out first named
subtype names as being names used in memebership tests and I don't see
any such tests specific to types.

The obvious hack would be:

    declare
        x : Button;
    begin
        if Button'Class(x) in Component'Class then ... end if;
    end;

/Jon

-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com

Re: Alright, now for an Ada '95 question.

[William W Pritchett]

Try something like the following code

  if target in Button'class then
     ...

But if you're doing Event handling in AppletMagic there is an easier way
to check for a particular widget

  if The_Event.Target = Object_Ptr(My_Widget) then
     ...

where My_Widget is a Button_Ptr, MenuItem_Ptr, etc and The_Event is of type 
Event.Event_Ptr

Hope this helps,
Bill Pritchett
DCS Corporation

Tom Di Sessa (tdisessa@wpllabs.com) wrote:
: First of all, I want to thank the people who responded to my first(and
: rather unpolite) post.  Thank you.

: In Java, I am able to do this comparison:
: (target is of Class(Type) Component, and Class Button is is derived from
: Component)

: if (target instanceof Button) {...}

: Now, is there a way to do this comparison in Ada '95, if target was of
: type Component'Class and Button was a derived type from Component?

: -tom :)

: -- 


: +------------------------------------------------------------------+
: | Thomas G. Di Sessa           ||                                  |
: |   WPL Laboratories, Inc.     || Email: tdisessa@wpllabs.com      |
: |   Whitehall Offices, Suite 6 || Voice: 610.658.2362 ext. 227     |
: |   410 Lancaster Avenue       ||   Fax: 610.658.2361              |
: |   Haverford, PA  19041       ||                                  |
: +------------------------------------------------------------------+

Re: Alright, now for an Ada '95 question.

[Jon S Anthony]

In article <32134421.31CF@wpllabs.com> Tom Di Sessa <tdisessa@wpllabs.com> writes:

> In Java, I am able to do this comparison:
> (target is of Class(Type) Component, and Class Button is is derived from
> Component)
> 
> if (target instanceof Button) {...}
> 
> Now, is there a way to do this comparison in Ada '95, if target was of
> type Component'Class and Button was a derived type from Component?

    if Target in Button then...end if;

if you wanted to know if Target is "classified" as a button (a direct
instance of _some_ type derived directly or indirectly from Button
or Button itself) you write

    if Target in Button'Class then ... end if;

/Jon
-- 
Jon Anthony
Organon Motives, Inc.
1 Williston Road, Suite 4
Belmont, MA 02178

617.484.3383
jsa@organon.com

Re: Alright, now for an Ada '95 question.

[Tucker Taft]

Tom Di Sessa (tdisessa@wpllabs.com) wrote:

: First of all, I want to thank the people who responded to my first(and
: rather unpolite) post.  Thank you.

: In Java, I am able to do this comparison:
: (target is of Class(Type) Component, and Class Button is is derived from
: Component)

: if (target instanceof Button) {...}

: Now, is there a way to do this comparison in Ada '95, if target was of
: type Component'Class and Button was a derived type from Component?

   if target in Button'Class then 
      ...
   end if;

The above checks whether the tag of Target identifies the type
Button or anything derived from it.  

If we want to know whether the tag identifies Button itself, then:

   if target in Button then
      ...
   end if;

will perform that test.

: -tom :)

-Tuck ;-) ;-)

: | Thomas G. Di Sessa           ||                                  |
: |   WPL Laboratories, Inc.     || Email: tdisessa@wpllabs.com      |
: |   Whitehall Offices, Suite 6 || Voice: 610.658.2362 ext. 227     |
: |   410 Lancaster Avenue       ||   Fax: 610.658.2361              |
: |   Haverford, PA  19041       ||                                  |

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA