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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Bug reports for Win32Ada Binding
Date: 1996/08/31
Message-ID: <Dx06M3.Lru@world.std.com>#1/1
X-Deja-AN: 177632961
references: <01bb9466$01037740$24af1486@pc-phw.inel.gov>
 <dewar.841212450@schonberg> <01bb96cb$340fd180$24af1486@pc-phw.inel.gov>
organization: The World Public Access UNIX, Brookline, MA
newsgroups: comp.lang.ada
Date: 1996-08-31T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <01bb96cb$340fd180$24af1486@pc-phw.inel.gov>,
Paul Whittington <paul@sage.inel.gov> wrote:
>  function WinError_HRESULT_To_ObjBase_HRESULT is new
>    Ada.Unchecked_Conversion (Win32.WinError.HRESULT,Win32.ObjBase.HRESULT);

But both HRESULTs are integer types, and all integer types are
inter-convertible using a normal type_conversion.  (In fact, they're
both derived from the same thing, so they're inter-convertible for that
reason, too.)  So you can say:

    X: constant Win32.ObjBase.HRESULT := CoCreateInstance(...);
    if FAILED(Win32.WinError.HRESULT(X)) then ...

or:

    if FAILED(Win32.WinError.HRESULT(CoCreateInstance(...))) then ...

No need for UNCHECKED conversion.  (I assumed use_clauses above.)

It seems strange to me that these two HRESULTs are two different types,
though, rather than subtypes of the same type.  Subtypes would be more
convenient because no conversion is requied.  But I haven't seen the
whole thing, so I don't know why they designed it that way.

- Bob