Passing variables to a subroutine

Hi everyone,

I'm trying to write a program that involves passing out some variables to a sub-routine to calculate some other variables. Here is the code:

Code:

#include <stdio.h>
#include <math.h>

int main (int argc, const char * argv[]) {

	double T;
	double r[7][4], k[7][4], A[7] = { 1, 2, 3, 4, 5, 6, 7}, Ea[7] = { 10, 20, 30, 40, 50, 60, 70}, K[2][4], Ad[2], Ead[2];

	void rateConstants(double k[7][4], double A[7], double Ea[7], double T);

        T = 443.15;	

	rateConstants(k, A, Ea, T);
	
	printf("\n %lf \n", k[1]);
	
    return 0;
}

void rateConstants(double k[7][4], double A[7], double Ea[7], double T)
{
	int i, j;
		  
	j = 0;
	
	for (i=0; i<6; i++)
	{
		k[i][j] = A[i]*exp(-Ea[i]/(8.31*T));
		
		printf("\n %lf", k[i][j]);  
			  
	}

}

As you can see, the subroutine prints out each value of k[i][j] that it calculates, then I have the main routine print out one of the k values to check if it's stored.However, the readout I actually get is:

0.997288
1.989167
2.975660
3.956787
4.932572
5.903034
-1.997117
logout

It doesn't matter what k value I choose, they all come out as -1.997117. Can anyone see what I'm doing wrong? I wrote a similar program for a much simpler case (as a test), and it all seemed to work.

I should warn you that I am not a brilliant programmer, so you may have to explain things to me quite explicitly.

Thanks in advance!

Code:

	printf("\n %lf \n", k[1]);

k[1] is not a double value

should be

Code:

	printf("\n %lf \n", k[1][0]);

or

Code:

	printf("\n %lf \n", *k[1]);

if you wish

Kurt

Thank you very much! It's the first option that I want - I really should have noticed that.

Also, is there an easier way to operate on/print out an array than the loop I have in the subroutine?

Sam

Originally Posted by shaig

is there an easier way to operate on/print out an array than the loop I have in the subroutine?

I'd say that any operation on an array involves some kind of loop.
Kurt

OK, thanks for the help!

Sam

When printing out doubles with printf(), %f should be used, not %lf. In the older (and generally currently implemented) C standard, %lf in printf() is not defined. While a lot of C libraries support %lf to mean %f, there's no guarantee, and it's certainly possible that you might run across an implementation that doesn't know what to do with %lf.

%lf should still be used for doubles with scanf(), though.