Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!van-bc!rsoft!mindlink!a563
From: a563@mindlink.UUCP (Dave Kirsch)
Newsgroups: comp.os.msdos.programmer
Subject: Re: #define thisneatmacro
Message-ID: <3580@mindlink.UUCP>
Date: 18 Oct 90 02:45:44 GMT
Organization: MIND LINK! - British Columbia, Canada
Lines: 71

> ctl8588@rigel.tamu.edu writes:
> 
> Msg-ID: <9286@helios.TAMU.EDU>
> Posted: 18 Oct 90 20:10:01 GMT
> 
> Org.  : TAMU
> Person: LAUGHLIN, CHET
> 
> I have a function that is called all the time by my screen handling
> routines in a program.  I'm not sure if TC is placing the two liner
> function inline even though I've set it for speed (vs. size) optimizing.
> I have been unable to write the function as a macro for all situations-
> possibly somebody knows a hack?
> 
> static void drawch(x,y,ch)
>   int x,y;
>   char ch;
> {
>   gotoxy(x,y);
>   cput(ch);
> }
> 
> I tried useing the following macro, with some success...
> 
> #define drawch(A,B,C)  {gotoxy(A,B); cput(C);}
> 
> however, the following code won't work...compiler doesn't like
> the extra ; at the end of drawch...
> 
> if (cond)
>    drawch(x,y,ch);
> else
>    printf("ICK!\n");
> 
> Any ideas out there?

Yeah, try this:

#define drawch(A, B, C) (gotoxy((A), (B)), cput((C)))

That should work in all cases, i.e. the if you showed will work. Because you
used the braces { }, the if was terminated with a ; after the last brace.  In
your previous macro, it expanded to:

if (cond)
  {gotoxy(x,y); cput(ch);};  /* NOTE extra semicolon!!! */
else
  printf("ICK!\n");

What happened is after the macro expanded, it leaves the semi-colon after the
macro in place, so the if statement was terminated, leaving a "dangling" else
statement that the compiler has no idea what to do with.

With the macro I have defined to be used instead, it expands to:

if (cond)
  (gotoxy((x), (y)), cput((ch)));
else
  printf("ICK!\n");

Which will work correctly.  I have used the comma operator to put the two
function calls together, I also encased the arguments in parenthesis so there
will be no problems in expansion when using "strange" arguments.

--
--
/// Dave 'Zoid' Kirsch UUCP: {uunet,ubc-cs}!van-bc!rsoft!mindlink!a563
Voice: (604) 585-8844       a563@mindlink.UUCP
                            Zoid@cc.sfu.ca
                      Vancouver, British Columbia
"In-no-sense?  Nonsense!" - The Art Of Noise.