Re: Return by reference

["Matthew Heaney" <matthew_heaney@acm.org>]

In article <Pine.BSF.4.10.9911021905050.1386-100000@shell5.ba.best.com> 
, Brian Rogoff <bpr@shell5.ba.best.com>  wrote:

> I was going to use the "Rosen trick" to modify data in the Fmt each time
> "&" is called. Unfortunately, that requires making the full view of
> Format_Type limited and you run into the problem I described.
>
> Is there a cleaner way to implement that interface?

1) Privately implement the type as tagged, to make it a by-reference
type.

2) This allows you to invoke RM95 13.3 (16), to take the address of
parameter.

3) Pass the address to an instantiation of
System.Address_To_Access_Conversions, which gives you a variable view of
the parameter.


Note that there has been a subtle error running throughout this thread.
There is nothing wrong with returning a "by-reference" type as a
function return type; the error is returning a *limited* type.


--
Science is, foremost, a method of interrogating reality: proposing
hypotheses that seem true and then testing them -- trying, almost
perversely, to negate them, elevating only the handful that survive to
the status of a theory. Creationism is a doctrine, whose adherents are
interested only in seeking out data that support it.

George Johnson, NY Times, 15 Aug 1999