* Problem with controlled types
@ 1998-12-14 0:00 bourguet
1998-12-14 0:00 ` Robert A Duff
1998-12-14 0:00 ` Matthew Heaney
0 siblings, 2 replies; 6+ messages in thread
From: bourguet @ 1998-12-14 0:00 UTC (permalink / raw)
I've found a CD with Aonix ObjectAda 7.1 Special Edition and tried to
compile a program developped under gnat 3.10. I failed due to the
number of units limitation of the Special Edition :-( but in the
process I found and removed some gnat dependancies. There where place
I had put these dependancies knowingly (like using the os_lib package,
I understand Ada stream better now). But the following one is, IMHO,
the result of bugs in one of the compilers, probably gnat but I prefer
to ask here before report the problem.
with ada.finalization;
package Pkg is
type A is private;
-- operations on B
type B is private;
function Get_B (I: A) return B;
-- other operations on B
private
type A is new Ada.Finalization.Controlled with record
...
end record;
type B is new Ada.Finalization.Controlled with record
...
end record;
end pkg;
ObjectAda complain that the Get_B function is primitive on two tagged
types, and that is not allowed.
Gnat compile and run correctly (as A'Class contains only A and
B'Class only B, this is not strange).
Now, which one is correct?
-- Jean-Marc
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http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Problem with controlled types
1998-12-14 0:00 Problem with controlled types bourguet
@ 1998-12-14 0:00 ` Robert A Duff
1998-12-14 0:00 ` Matthew Heaney
1 sibling, 0 replies; 6+ messages in thread
From: Robert A Duff @ 1998-12-14 0:00 UTC (permalink / raw)
bourguet@my-dejanews.com writes:
> package Pkg is
>
> type A is private;
> -- operations on B
>
> type B is private;
>
> function Get_B (I: A) return B;
> -- other operations on B
>
> private
>
> type A is new Ada.Finalization.Controlled with record
> ...
> end record;
>
> type B is new Ada.Finalization.Controlled with record
> ...
> end record;
>
> end pkg;
>
> ObjectAda complain that the Get_B function is primitive on two tagged
> types, and that is not allowed.
>
> Gnat compile and run correctly (as A'Class contains only A and
> B'Class only B, this is not strange).
>
> Now, which one is correct?
ObjectAda.
- Bob
--
Change robert to bob to get my real email address. Sorry.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Problem with controlled types
1998-12-14 0:00 Problem with controlled types bourguet
1998-12-14 0:00 ` Robert A Duff
@ 1998-12-14 0:00 ` Matthew Heaney
1998-12-14 0:00 ` Tucker Taft
1998-12-14 0:00 ` Tom Moran
1 sibling, 2 replies; 6+ messages in thread
From: Matthew Heaney @ 1998-12-14 0:00 UTC (permalink / raw)
bourguet@my-dejanews.com writes:
> with ada.finalization;
>
> package Pkg is
>
> type A is private;
> -- operations on B
>
> type B is private;
>
> function Get_B (I: A) return B;
> -- other operations on B
>
> private
>
> type A is new Ada.Finalization.Controlled with record
> ...
> end record;
>
> type B is new Ada.Finalization.Controlled with record
> ...
> end record;
>
> end pkg;
>
> ObjectAda complain that the Get_B function is primitive on two tagged
> types, and that is not allowed.
>
> Gnat compile and run correctly (as A'Class contains only A and
> B'Class only B, this is not strange).
>
> Now, which one is correct?
GNAT is correct; ObjectAda is incorrect.
An operation cannot be primitive for more that one type is only true for
(publicly) tagged types. Since A and B and not publically tagged,
Get_B is a legal operation.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Problem with controlled types
1998-12-14 0:00 ` Matthew Heaney
@ 1998-12-14 0:00 ` Tucker Taft
1998-12-14 0:00 ` Robert I. Eachus
1998-12-14 0:00 ` Tom Moran
1 sibling, 1 reply; 6+ messages in thread
From: Tucker Taft @ 1998-12-14 0:00 UTC (permalink / raw)
Matthew Heaney (matthew_heaney@acm.org) wrote:
: bourguet@my-dejanews.com writes:
: > with ada.finalization;
: >
: > package Pkg is
: >
: > type A is private;
: > -- operations on B
: >
: > type B is private;
: >
: > function Get_B (I: A) return B;
: > -- other operations on B
: >
: > private
: >
: > type A is new Ada.Finalization.Controlled with record
: > ...
: > end record;
: >
: > type B is new Ada.Finalization.Controlled with record
: > ...
: > end record;
: >
: > end pkg;
: >
: > ObjectAda complain that the Get_B function is primitive on two tagged
: > types, and that is not allowed.
: >
: > Gnat compile and run correctly (as A'Class contains only A and
: > B'Class only B, this is not strange).
: >
: > Now, which one is correct?
: GNAT is correct; ObjectAda is incorrect.
: An operation cannot be primitive for more that one type is only true for
: (publicly) tagged types. Since A and B and not publically tagged,
: Get_B is a legal operation.
Not quite true. The problem is that *inside* the package private
part and the body, Get_B is primitive on two tagged types,
and that is not legal.
So ObjectAda wins this round ;-).
--
-Tucker Taft stt@inmet.com http://www.inmet.com/~stt/
Intermetrics, Inc. Burlington, MA USA
An AverStar Company
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Problem with controlled types
1998-12-14 0:00 ` Tucker Taft
@ 1998-12-14 0:00 ` Robert I. Eachus
0 siblings, 0 replies; 6+ messages in thread
From: Robert I. Eachus @ 1998-12-14 0:00 UTC (permalink / raw)
In article <F3z2s2.6CG.0.-s@inmet.camb.inmet.com> stt@houdini.camb.inmet.com (Tucker Taft) writes:
> Not quite true. The problem is that *inside* the package private
> part and the body, Get_B is primitive on two tagged types,
> and that is not legal.
> So ObjectAda wins this round ;-).
Interesting. Try the following example:
generic
type Out_Type is private;
type In_Type is new Out_Type;
function Conversion(I: In_Type) return Out_Type;
with Ada.Finalization; with Conversion;
package Pkg is
type A is private;
package Inner is
type B is private;
function Convert is new Conversion(A,B);
-- I'd use Ada.Unchecked_Conversion but that has convention Intrinsic.
private
type B is new Ada.Finalization.Controlled with record
...
end record;
end Inner;
private
type A is new Ada.Finalization.Controlled with record
...
end record;
end Pkg;
Now according to Tucker, in the private part of Pkg, Convert is a
dispatching operation of A, and in the private part of Inner, it is a
dispatching operation of B. As written there is no body allowed so
the example is legal. I could add types C and D and other generic
instantiations to play futher with this.
I don't think I like either interpretation of 3.9.2(12).
Seriously, 3.9.2(12) says: "A given subprogram shall not be a
dispatching operation of two or more distinct tagged types." It
doesn't say of two visibly tagged types, so I think my example would
also be illegal.
--
Robert I. Eachus
with Standard_Disclaimer;
use Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Problem with controlled types
1998-12-14 0:00 ` Matthew Heaney
1998-12-14 0:00 ` Tucker Taft
@ 1998-12-14 0:00 ` Tom Moran
1 sibling, 0 replies; 6+ messages in thread
From: Tom Moran @ 1998-12-14 0:00 UTC (permalink / raw)
>An operation cannot be primitive for more that one type is only true for
>(publicly) tagged types. Since A and B and not publically tagged,
>Get_B is a legal operation.
Interesting. Then
procedure P(x: in A; y: in B);
would be legal? What would it do?
^ permalink raw reply [flat|nested] 6+ messages in thread
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1998-12-14 0:00 Problem with controlled types bourguet
1998-12-14 0:00 ` Robert A Duff
1998-12-14 0:00 ` Matthew Heaney
1998-12-14 0:00 ` Tucker Taft
1998-12-14 0:00 ` Robert I. Eachus
1998-12-14 0:00 ` Tom Moran
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