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From: stt@houdini.camb.inmet.com (Tucker Taft)
Subject: Re: ObjectAda vs Gnat -- bugs
Date: 1997/05/19
Message-ID: <EAEMqA.31A.0.-s@inmet.camb.inmet.com>#1/1
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Organization: Intermetrics, Inc.
Newsgroups: comp.lang.ada
Date: 1997-05-19T00:00:00+00:00
List-Id: <comp.lang.ada>


Tom Moran (tmoran@bix.com) wrote:

: I'm a little confused by this renaming of function return values.  If T
: is a limited type and F is a function returning T, then I understand one
: can:
:   X:T renames F(...);
: and one cannot
:   X:T := F(...);
: Is that correct?

Correct.

: If T is not limited, then what are the differences between
:   X : T renames F(...);
:   Y : T := F(...);

In the first case, X inherits the "constant"ness of the object
being renamed, which in this case, means that X is a constant.
In the second case, we have a new object, and since you left
off the word "constant" it is not a constant.

If you had written "Y : constant T := F(...);" then they would
be almost indistinguishable (though you wouldn't be able
to apply representation clauses to the rename, since you haven't
really declared a new object).

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Burlington, MA  USA

P.S. For what its worth, enumeration literals really are treated
as functions in our Ada 95 front end symbol table.  It is just 
their "body" which is a bit funny -- it is intrinsic and all calls
are "expanded" inline. -TT