Re: "PORTING C" > How to assign a value to a define statement?

"Bo Persson" <>
Wed, 3 Feb 2010 18:25:40 +0100
Robby wrote:


This question is geared more towards seeking a voice of programming

I am running into a situation where I need some advice on how to do
things. Perhaps I am seeing this the wrong way. In summary, from
main(), I would like to call a defined macro called
"Config_delay_timers", and in that macro I would like to do some
calculations where the result can be assigned to the value of
another #define statement.

Please view the following code:

#ifndef TEST_H
#define TEST_H

#define Config_delay_timers(extCrys, fpllidiv, fpllmul, fpllodiv) \


#endif // TEST_H //

#include <stdio.h>
#include "test.h"

int main()

Config_delay_timers(8, 2, 21, 8);

return 0;

I am getting an error where the compiler complains about FREQ is
undefclared. So how is one supposed to carry out a particular
calculation via a define macro and then further assign this result
to other define variables in the program.

Macros don't do variables, they are just text processing.

I am thinking of mayby using #ifdef preprocessor command but I
don't see how this would be of any use in this particular case.

All help or reccomendations is very welcome and apprciated. Thanks
in advance!

If you want a constant value in the program, declare one:

const float FREQ = ...

Bo Persson

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