From: "Pat Rogers" <progers@NOclasswideSPAM.com>
Subject: Re: "out" or "access"
Date: 1998/10/22
Date: 1998-10-22T00:00:00+00:00 [thread overview]
Message-ID: <70nhch$nhr$1@supernews.com> (raw)
In-Reply-To: 70l1nq$mrb$1@cnn.Princeton.EDU
Martin C. Carlisle wrote in message
<70l1nq$mrb$1@cnn.Princeton.EDU>...
>Be careful using access as below, as this creates two different
>dispatched objects in the call (which is illegal). See LRM 6.1(24)
>and 3.9.2
You seem to be saying that there is no legal call with this
approach, but neither RM reference supports that conclusion.
The actual parameters to a call make a given call illegal or not,
and that depends upon what is passed, per call. For example, if the
actuals are statically-tagged -- the typical case -- there is no
problem. If both actuals are dynamically-tagged they have to have
the same tag, which is checked at run-time per RM 3.9.2(16). A call
cannot have both statically-tagged and dynamically-tagged
controlling operands, per RM 3.9.(8), but that is just one case.
>> type T1 is tagged ...
>>
>> type T1_Pointer is access T1;
>>
>> procedure Foo( This : in T1; That : in T1_Pointer );
>>
>>Then, in a derivation:
>>
>> type T2 is new T1 with ...
>>
>>This gives us:
>>
>>
>> procedure Foo( This : in T2; That : in T1_Pointer );
>>
>>Note that the type of the formal 'That' is still T1_Pointer,
>>probably not what we wanted.
>>
>>On the other hand, had we defined things as:
>>
>> type T1 is tagged ...
>>
>> -- don't need this now... type T1_Pointer is access T1;
>>
>> procedure Foo( This : in T1; That : access T1 );
>>
>>The derivation would provide
>>
>> procedure Foo( This : in T2; That : access T2 );
>>
>>which is probably the desired result in this case.
---
Pat Rogers Training & Development in:
http://www.classwide.com Deadline Schedulability Analysis
progers@acm.org Software Fault Tolerance
(281)648-3165 Real-Time/OO Languages
next prev parent reply other threads:[~1998-10-22 0:00 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-10-21 0:00 "out" or "access" =:-) Vincent
1998-10-21 0:00 ` Jeff Carter
1998-10-21 0:00 ` Pat Rogers
1998-10-21 0:00 ` Martin C. Carlisle
1998-10-22 0:00 ` Pat Rogers [this message]
1998-10-22 0:00 ` Robert A Duff
1998-10-21 0:00 ` dennison
1998-10-21 0:00 ` Tucker Taft
1998-10-22 0:00 ` Pascal Obry
1998-10-29 0:00 ` Robert A Duff
1998-10-29 0:00 ` Matthew Heaney
1998-10-29 0:00 ` Robert A Duff
1998-10-30 0:00 ` dennison
1998-10-30 0:00 ` Matthew Heaney
1998-10-30 0:00 ` Robert A Duff
1998-10-31 0:00 ` dewar
1998-10-31 0:00 ` Matthew Heaney
1998-10-31 0:00 ` Matthew Heaney
1998-11-01 0:00 ` Robert A Duff
1998-11-01 0:00 ` Matthew Heaney
1998-11-01 0:00 ` Robert A Duff
1998-11-02 0:00 ` Matthew Heaney
1998-11-03 0:00 ` Simon Wright
1998-11-16 0:00 ` Matthew Heaney
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox