Need to return an array from a function.

[silverdace]

Hi I am trying to learn C as part of my research. I need to return two arrays from a function. How do I take arrays as arguments and then let the function operate on those arrays and then return the modified arrays?


Here is the function code :

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

#include "Head.h"

void gaussleg128(double X1, double X2, double X[], double W[], int N)
{

double Z1, Z, XM, XL, PP, P1, P2, P3;
int I, J, M;

M = ((N + 1) / 2) - ((N + 1) % 2);
XM = 0.5 * (X1 + X2);
XL = 0.5 * (X2 - X1);
for (I = 1; I <= M; I++) {
Z = cos((PI * (I - 0.25)) / (N + 0.5));
do { P1 = 1.0;
P2 = 0.0;
for (J = 1; J <= N; ++J)
{
P3 = P2;
P2 = P1;
P1 = ((2.0 * J - 1.0) * Z * P2 - (J - 1.0) * P3) / J;
}
PP = N * (Z * P1 - P2) / (pow(Z, 2.0) - 1.0);
Z1 = Z;
Z = Z1 - P1 / PP;
} while (fabs(Z - Z1) <= EPS);
X = XM - XL * Z;
X[N + 1 - I] = XM + XL * Z;
W = 2.0 * XL / ((1.0 - pow(Z, 2.0)) * pow(PP, 2.0));
W[N + 1 - I] = W;
}
}
And here is the "main" code.

/* 3D Scattering */

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


#include "Head.h"


int main ()

{
extern double abs128[128], wt128[128], dist[9];
double radius, dmf, mass, X, pmin1, pmin3, recmass1, recmass3, W1, W2, moments[9][9], norm1, norm3;
int k, I, t, k2, intval[9];

for (t = 0; t <= 128; t++)
abs128[t] = 0.0;
wt128[t] = 0.0;


gaussleg128(-1.0, 1.0, abs128, wt128, 128);

plus rest of prog.............

 

[jstreich]

By default arrays are passed as pointers, so for simplicy assume that arrays are always passed by reference... Any changes made to an array in another scope are seen in the calling function.

So what your doing should show the changes to rest of the program...

For future reference, code snipets posted are easier to read if enclosed in code tags so that spaceing is preserved.