OK, so I want to make it so that I do not have to keep typing in "ch->race == race_lookup("vampire")" every time I want to check and see if someone is a vampire. Now, I want to put it in the merc.h file (or our equivalent).

Now, I think I've got it right, but want to make sure. I want it to check if they are a vampire, regardless of if they are a PC or NPC. It should be:

#define IS_VAMPIRE(ch) (ch->race == race_lookup("vampire"))

That's correct right? That would allow me to simplify "ch->race == race_lookup("vampire")" to IS_VAMPIRE correct?

Arholly

Nevermind, yes I am.

IIRC correctly it should look like:

#define IS_VAMPIRE(ch) ((ch)->race == race_lookup("vampire"))

without putting ch in () it will use the literal ch, as in it will only work if you have a ch variable defined in the local scope. surrounding it with () means that you can do IS_VAMPIRE(victim) and it will still work.

but it has been a long time since i used c so could be all wrong :P

Wrong, I believe. Wrapping it in parentheses just ensures that the syntax of what you pass to the macro doesn't interfere with the syntax of the macro itself.

Yeah… no, that's completely wrong. :wink: It has nothing at all to do with local scope etc.

It has to do with the fact that a macro isn't a function, and so the substitution occurs literally.

consider:

#define SQUARE(x) (x * x)

now:

SQUARE(1+2)

expands to

(1+2 * 1+2)

which yields 5 rather than the expected result 9.

The safe parenthesization of the parameters,

#define SQUARE(x) ((x) * (x))

makes sure that the expression is evaluated as expected.

Of course, if x happens to be a function call, that function call will still be made twice, again unlike if SQUARE were a function. But that's a problem for another day.

People tend to think of macros as functions, which they really aren't at all; they're just a syntactic transformation.

I avoid macros in C whenever reasonable to do so.

i had a sneaky suspicion that i was talking complete bullshit :P

True, macros don't typically get added to the symbol table so debugging can be difficult. Also, in C++ preprocessor macros don't have a scope/namespace.

You can achieve this using a function just the same:

bool is_vampire( CHAR_DATA *ch )
{
  if( !ch || !ch->race )
    return FALSE;

  if( ch->race == race_lookup("vampire") )
    return TRUE;
  return FALSE;
}

bool is_vampire( CHAR_DATA *ch ) {
  assert(ch && ch->race);
  return ch->race == race_lookup("vampire"); 
}