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From: dan@dyndata.UUCP (Dan Everhart)
Newsgroups: comp.lang.c++
Subject: Re: #defines....
Message-ID: <686@dyndata.UUCP>
Date: 5 Jul 90 17:51:03 GMT
References: <37786@genrad.UUCP><PCG.90Jul2225948@odin.cs.aber.ac.uk>
Reply-To: dan@dyndata.UUCP
Organization: Dynamic Data & Electronics, Edmonds WA
Lines: 35
In-reply-to: slp@genrad.uucp's message of 2 Jul 90 14:54:50 GMT



In article <37786@genrad.UUCP> slp@genrad.uucp (Steven L. Peters) writes:
>   With the C++ const, enum, and inline declarations, is it ever
>   necessary to use #define in a C++ program? 

I don't know about *necessary* but I find it convenient to use the
following:  

#if defined(DEBUG)
#define pure	{ DebuggerTrap (); }
#else
#define	pure	= 0
#endif

class Xyz
   {
   // ...
   virtual f () pure;
   // ...
   } 

This quickly finds erroneous calls of pure virtual functions during
debugging, yet leaves no overhead in a production version.  It's also
highly readable.

In article <PCG.90Jul2225948@odin.cs.aber.ac.uk> pcg@cs.aber.ac.uk (Piercarlo Grandi) writes:
>   arguable that 'this' (which should not exist, however) should be a
>   reference and not a pointer, but it's too late to change that.

A #define comes in handy here too:

#define self (*this)

I don't think you could do either of these tricks without using a #define.