> class B
> extends A;
> Real y; // double definition?
> B.B b; // This would not be needed for stack overflow
> end B;
So you believe that the following class should actually work? (It won't,
for sure)
class A
A a;
end A;
And regarding
package Test
class A
extends B;
Real x;
class B
extends A;
Real y; // double definition?
end B;
end A;
end Test;
class A
Test.A a;
Test.A.B b;
end A;
What do you think the output should be? We could possibly guard against
extending the same class with the same modification more than once.
(extends A(x=5); extends A(x=6); should produce double definitions.
extends A(x=5); extends A(x=5); should not).
--
Martin Sjölund
On 2010-11-17 08:43, Christoph Höger wrote:
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Hi all,
the following example produces a stack overflow in omc 1.5.0.svn.r5700-1.deb
package Test
class A
extends B;
Real x;
class B
extends A;
Real y; // double definition?
B.B b; // This would not be needed for stack overflow, but
should be correct too
end B;
end A;
end Test;
I am not quite sure, why the extension from inner classes is even
allowed (maybe for some fancy type constructs), but the specification is
quite clear on that point. This is a little bit complicated, but from my
POV it should work that way:
- - when B is looked up from "extends B" in A, the "partially flattened"
environment of A is used in B which yields scope(B) = { 'B' = Test.A.B,
'x' = Real, y = 'Real', b = 'Test.A.B' }
- - when B is looked up itself, the above scope is handed down, which
_might_ result in a "double definition" error for y but at least should
succeed in type creation.
Basically the problem arises with circular inheritance, which would in
general require a fixed point analysis. But since the specification
simply states that the type names in extends clauses are looked up
ignoring all other extends clauses, it should work.
best regards,
Christoph
- --
Christoph Höger
Technische Universität Berlin
Fakultät IV - Elektrotechnik und Informatik
Übersetzerbau und Programmiersprachen
Sekr. TEL12-2, Ernst-Reuter-Platz 7, 10587 Berlin
Tel.: +49 (30) 314-24890
E-Mail: [email protected]
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