Version 1.2 of ais/ai-00191.txt

!section 3.3(4)
!subject An OBJECTive View
!reference RM95-3.3(4), 6.2(2), 6.4.1(10)
!from Dan Lehman 97-05-08
!keywords object, formal parameter, view
!reference 1997-15750.a Dan Lehman 1997-5-8>>
!discussion

RM95-3.3(2 & 4) state:

   All of the following are objects:
     a formal parameter of a subprogram, entry, or generic subprogram;

but RM95-6.2(2) & 6.4.1(10) contradict this in stating:

   When a parameter is passed by reference, the formal parameter denotes
   (a view of) the object denoted by the actual parameter; ...

   For a formal parameter (of any mode) that is passed by reference (see 6.2),
   a view conversion of the actual parameter to the nominal subtype of the
   formal parameter is evaluated, and the formal parameter denotes that
   conversion.

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Appendix

>>> From lehman@ida.org Mon Jul 10 23:17:36 1995

   In an aside on this FRN, I asked Bob how the overriding body with the
one abstract (and one not) parameter could be called, given 3.9.3(1):

| > B> The overriding body, however, could be called ...
| >
|D> What happens then, when in elaboration an attempt to create an object
|D> of an abstract type (formal parameter) is made?  --Program_Error?
|
|We have a non-abstract subprogram one of whose parameters is of an
|abstract type.  The subprogram is not primitive of that abstract type.
|How can you call it?
|
|You can't create an object of an abstract type.  But you can create a
|view of an object, and the view can be of the abstract type.  Create an
|object of some descendant of the abstract type.  Use type conversion to
|create a view whose type is the abstract type, and pass that to the
|subprogram.  Why you would want to do this, I don't know.
|
|Note that formal parameters of a tagged type are not objects in their
|own right; they are just views.  6.4.1(10).

   Since 3.3(4) gives a somewhat different view, one might object. [sorry]
Should this have an AI-ish note of explanation--to qualify 3.3(4) to mean
"... formal parameter that is passed by copy ..."?

---Dan
------- *

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>>> From bobduff@world.std.com Tue Jul 11 15:08:14 1995

>    Since 3.3(4) gives a somewhat different view, one might object. [sorry]

:-)

> Should this have an AI-ish note of explanation--to qualify 3.3(4) to mean
> "... formal parameter that is passed by copy ..."?

Yeah, I guess so.

- Bob

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