Thread: Constants

i have defined constants in a header file

//Define constants

#define Grids 70
#define Hori_L 1.0
#define delta_x Hori_L*pow((Grids - 1), -1) //m

However when i call them in my .cc files I need to place a bracket around them (delta_x). Why is that?

Cheers

Why you shouldn't use #define here.

What happens when you use constants without brackets? What error messages do you get?

If only the third one is the problem:

Code:

#define delta_x Hori_L*pow((Grids - 1), -1) //m

Then you need to remove the comment from it because it may cause problems like this:

Code:

#define Grids 70
#define Hori_L 1.0
#define delta_x Hori_L*pow((Grids - 1), -1) //m

int main(int argc, char **argv) {
    printf("%d\n", delta_x);
    return 0;
}

will become this after preprocessing:

Code:

#define Grids 70
#define Hori_L 1.0
#define delta_x Hori_L*pow((Grids - 1), -1) //m

int main(int argc, char **argv) {
    printf("%d\n", Hori_L*pow((Grids - 1), -1) //m);
    /*notice that the end of the statement gets cut off*/
    return 0;
}

and you should have brackets around that anyway, so that the order of operations doesn't get messed up


it should look like this:

Code:

#define delta_x (Hori_L*pow((Grids - 1), -1))

you could add C-style comments and be ok.

Code:

#define delta_x (Hori_L*pow((Grids - 1), -1)) /*m*/