TITLE: advice on when to use macros

PROBLEM: swampwiz@ix.netcom.com(Jean P. Laborde )

Someone responded to this group and advocated using a define macro.

I thought that was extremely bad practice in C++.


RESPONSE: <bbogard@ibm.net>

Using #define macros is not a bad idea, but it depends on the problem and
restrictions of the project you are working on.  Sometime, for speed you
want just a macro and not have to make a function call.


RESPONSE: kcline@sun152.spd.dsccc.com (Kevin Cline), 22 Feb 96

Using macros to define functions is a very bad idea.  Use inline functions
instead.  This allows the compiler to decide whether inlining the code
is faster than a function call.  The compiler knows more about this than
the programmer.  Also, inline functions calls are typesafe.

Macros should only be used for text-processing tricks that improve
code maintainability, e.g.

    #define FRUIT_LIST \
	    FRUIT(apple), \
	    FRUIT(orange), \
	    FRUIT(pear)

    #define FRUIT(t) t
    typedef enum { FRUIT_LIST } Fruit;  [ corrected. -adc]
    #undef FRUIT

    // #t produces a quoted string 
    #define FRUIT(t) #t
    static const char* const FruitNameTable[] = { FRUIT_LIST };  [ corrected ]
    #undef FRUIT

When the list gets long, techniques like this can be useful for
reducing redundancies in source code.  I find that as soon
as I have to specify the same thing twice, and the compiler is unable
to make sure they match, they won't. 

[ Amen. -adc ]