🔒 Locked

using #defined values

Started by oveja-carnivora Jun 1, 2002 at 11:44 PM 20 replies 1k views

Original Post

Jun 1, 2002 at 11:44 PM

can anybody tell me why I cant divide by a #defined value? ex- This C++ syntax doesnt work: #define X 5 long Y = 3; long Z = Y/X; but this does: #define X 5 long Y = 3; long Z = Y/(X+0); Thanks, Ben

Null and Void

163

Null and Void

Jun 1, 2002 at 11:50 PM

That are both valid examples. What do you mean by "doesn''t work"?

zealouselixir

157

zealouselixir

Jun 1, 2002 at 11:53 PM

You shouldn''t be surprised that both of those set Z equal to 0. It''s a result of truncation. If that''s not the trouble you''re having, then I''m sorry if I''ve underminded your intelligence.

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

[if you have a link proposal, email me.]

oveja-carnivora

Author

oveja-carnivora

Jun 2, 2002 at 12:00 AM

I mean that it gives me a syntax error on the character after the #defined value, my actualy code is:

#define LoadStepNum
...
long LoadBarProgress = 0;
...
LoadBarProgress += screenwidth / (LoadStepNum + 0);

without the () and the + 0 it gives me a syntax error on the '';''

this doesnt make any sense, so thanks for the help

-Ben

Melraidin

Jun 2, 2002 at 12:09 AM

Only thing I notice is that you don''t have anything defined for LoadStepNum. Make sure there''s a number in there, and make sure that you''ve got it written as:

#define LoadStepNum 7

No equal sign or anything...

Although I''m betting you''ve already got it like this and it was simply a copying error.

oveja-carnivora

Author

oveja-carnivora

Jun 2, 2002 at 12:22 AM

wow do I feel stupid, I was sure I typed a 4 there.
ack

I think I will go hide until this message is forgotten.

Xai

344

Xai

Jun 2, 2002 at 12:31 AM

bump

elis-cool

108

elis-cool

Jun 2, 2002 at 2:52 AM

lol... bump

Well I have done similer things... note similer, but in no way was it near this stupid!!

CEO Plunder Studios

zealouselixir

157

zealouselixir

Jun 2, 2002 at 2:08 PM

Heh. How did you not notice the "divide-by-zero" errors you were getting?

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

[if you have a link proposal, email me.]

oveja-carnivora

Author

oveja-carnivora

Jun 2, 2002 at 2:11 PM

I wasnt getting any, just the syntax errors. not very intelegent error message, but not a very intelegent thing to be doing so oh well

quote:
Original post by ZealousElixir
Heh. How did you not notice the "divide-by-zero" errors you were getting?

[edited by - oveja-carnivora on June 2, 2002 3:14:27 PM]

zealouselixir

157

zealouselixir

Jun 2, 2002 at 2:21 PM

LoadBarProgress += screenwidth / (LoadStepNum + 0);

Without LoadStepNum defined, that would appear to the compiler as

LoadBarProgress += screenwidth / (+ 0);

and furthermore

LoadBarProgress += screenwidth / 0;

So, if you ran that code, how did you avoid a process-fatal error?

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

[if you have a link proposal, email me.]

oveja-carnivora

Author

oveja-carnivora

Jun 2, 2002 at 2:28 PM

That actualy never ran, it was a one of a bunch of errors that I was working thru. just trying to fix compiler errors

zealouselixir

157

zealouselixir

Jun 2, 2002 at 2:45 PM

I see.

JonStelly

Jun 2, 2002 at 2:56 PM

Well done fellas, very classy. Would you also like to mug my grandmother while you''re kicking this guy for having the nerve to make a mistake?

zealouselixir

157

zealouselixir

Jun 2, 2002 at 6:37 PM

"It takes a big man to cry, but it takes a bigger man to laugh at that man."

Classy it weren''t, but boys will be boys. I doubt seriously that your repremand, no matter how appropriate, will have the intended effect. Besides, he took our time, we take his pride. It would be fair enough to stop there, but we also gave him the ability to recognize stupid errors in the future.

No harm intended.

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

[if you have a link proposal, email me.]

Jason2Jason

Jun 2, 2002 at 6:42 PM

would using a const long instead of a #define be better? I''m prob wrong so ignor me if I am. Its just i read somewhere that its ment to be ''better practice'' to use const''s and not #define''s in C++. I still don''t completely follow that tho.

-J

zealouselixir

157

zealouselixir

Jun 2, 2002 at 6:47 PM

Macros are evil for three reasons. See the C++ FAQ Lite for more info. For single values, const variables are more desirable, but they require you do use extern and to define the const in a single translation unit, whereas #define can be simply tossed into a

Wait a minute. const values DON'T require you to use extern, do they?

Never mind.

Anyway, macros are evil, and yes, in this situation, it would have been better to use const (certainly would have eliminated the need for this thread...

)

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

[if you have a link proposal, email me.]
EDITED for schtuff.

[edited by - zealouselixir on June 2, 2002 7:48:53 PM]