🚀 go-pugleaf

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
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