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From: tknarr@xmission.com  ( Todd Knarr )
Subject: Re: Hungarian notation
Date: 1996/01/09
Message-ID: <4csi2t$gsa@news.xmission.com>#1/1
X-Deja-AN: 134548094
references: <30C40F77.53B5@swsbbs.com> <30EF0415.6FE1@tus.ssi1.com>
 <1996Jan7.045815.8676@ohstpy> <4cpb00$nqk@news.xmission.com>
 <4crm6i$24mi@navajo.gate.net>
organization: Chaos Central
reply-to: tknarr@xmission.com ( Todd Knarr )
newsgroups: 
 comp.lang.eiffel,comp.lang.ada,comp.edu,comp.lang.c,comp.lang.c++,comp.lang.modula2,comp.lang.modula3
Date: 1996-01-09T00:00:00+00:00
List-Id: <comp.lang.ada>

In <4crm6i$24mi@navajo.gate.net>, feathers@gate.net (Michael Feathers) writes:
>I've never seen a variable that can be any of 9 different types in C++.
>All variables have a type.  Period.  A type can be a union or a base 
>class, but all variables have one and only one type in C++.  If you don't
>believe me, check the ARM.

You haven't worked with polymorphic classes as reference arguments or
pointers much, then. I have the following class heirarchy:

Stall
        AvailableStall
        AssignedStall
        OccupiedStall
        DirtyStall
        BeingCleanedStall
        BrokenStall
        OutOfServiceStall
        AlarmStall
        OfflineStall

That's 9 subclasses of Stall. I do, though, routinely have arguments that
are pointers or references to Stall. The actual object may be any one of
those 9 subclasses.

Give me an HN prefix that tells me that, in the following prototype

Stall *HardwareChangeSignalled( Stall& ExistingStall, int ByteCount,
                                unsigned char *aHardwareData );

the ExistingStall argument is one of the 9 subclasses and never a Stall,
and the returned pointer is one of the 9 subclasses and never a pointer to
Stall.

Without such a prefix, you can readily get the obnoxious situation of a new
programmer depending on the prefix and not realizing that he is dealing with
a polymorphic type. This can cause him problems if he refers to the source
code for Stall, depending on the HN prefix to be the actual type.

--
Todd Knarr : tknarr@xmission.com      |  finger for PGP public key
                                      |  Member, USENET Cabal

Seriously, I don't want to die just yet.  I don't care how
good-looking they are, I! don't! want! to! die!"
                                        -- Megazone ( UF1 )