NAG Library Manual, Mark 28.6
```/* nag_matop_complex_gen_matrix_fun_usd (f01fmc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.6, 2022.
*/
#include <math.h>
#include <nag.h>

#ifdef __cplusplus
extern "C" {
#endif
static void NAG_CALL f(Integer m, Integer *iflag, Integer nz, const Complex z[],
Complex fz[], Nag_Comm *comm);
#ifdef __cplusplus
}
#endif

int main(void) {

/* Scalars */
Integer exit_status = 0;
Integer i, iflag, j, n, pda;

/* Arrays */
static double ruser[1] = {-1.0};

Complex *a = 0;

/* Nag Types */
Nag_Comm comm;
Nag_OrderType order;
NagError fail;

INIT_FAIL(fail);

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
order = Nag_RowMajor;
#endif

printf("nag_matop_complex_gen_matrix_fun_usd (f01fmc) ");
printf("Example Program Results\n\n");

/* For communication with user-supplied functions: */
comm.user = ruser;

fflush(stdout);

/* Skip heading in data file */
scanf("%*[^\n]");

/* Read in the problem size */
scanf("%" NAG_IFMT "%*[^\n]", &n);

pda = n;

if (!(a = NAG_ALLOC((pda) * (n), Complex))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read in the matrix a from data file */
for (i = 1; i <= n; i++)
for (j = 1; j <= n; j++)
scanf(" ( %lf , %lf ) ", &A(i, j).re, &A(i, j).im);
scanf("%*[^\n]");

/* Find matrix function using
* nag_matop_complex_gen_matrix_fun_usd (f01fmc)
* Function of a complex matrix
*/
nag_matop_complex_gen_matrix_fun_usd(order, n, a, pda, f, &comm, &iflag,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_matop_complex_gen_matrix_fun_usd (f01fmc)\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Print solution using
* nag_file_print_matrix_complex_gen (x04dac).
* Print complex general matrix (easy-to-use)
*/
nag_file_print_matrix_complex_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag,
n, n, a, pda, "f(A)", NULL, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_complex_gen (x04dac)\n%s\n",
fail.message);
exit_status = 2;
goto END;
}

END:
NAG_FREE(a);
return exit_status;
}

static void NAG_CALL f(Integer m, Integer *iflag, Integer nz, const Complex z[],
Complex fz[], Nag_Comm *comm) {
/* Scalars */
Integer j;
#ifdef _OPENMP
#pragma omp master
#endif
if (comm->user[0] == -1.0) {
printf("(User-supplied callback f, first invocation.)\n");
fflush(stdout);
comm->user[0] = 0.0;
}
for (j = 0; j < nz; j++) {
/* The m^th derivative of exp(3z) for complex z */
fz[j].re = pow(3.0, m) * exp(3.0 * z[j].re) * cos(3.0 * z[j].im);
fz[j].im = pow(3.0, m) * exp(3.0 * z[j].re) * sin(3.0 * z[j].im);
}
/* Set iflag nonzero to terminate execution for any reason. */
*iflag = 0;
}
```