NAG Library Manual, Mark 30.1
```/* nag_lapackeig_dtgsyl (f08yhc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.1, 2024.
*/

#include <nag.h>
#include <stdio.h>

int main(void) {
/* Scalars */
double dif, scale;
Integer i, ijob, j, m, n, pda, pdb, pdc, pdd, pde, pdf;
Integer exit_status = 0;

/* Arrays */
double *a = 0, *b = 0, *c = 0, *d = 0, *e = 0, *f = 0;
char nag_enum_arg[40];

/* Nag Types */
NagError fail;
Nag_OrderType order;
Nag_TransType trans;

/* K(I,J) maps matrix element (I,J) to array storage element k */
#ifdef NAG_COLUMN_MAJOR
#define K(I, J, PD) (J - 1) * PD + I - 1
order = Nag_ColMajor;
#else
#define K(I, J, PD) (I - 1) * PD + J - 1
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_lapackeig_dtgsyl (f08yhc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &m, &n);
scanf("%" NAG_IFMT "%*[^\n]", &ijob);
if (m < 0 || n < 0 || ijob < 0 || ijob > 4) {
printf("Invalid m, n or ijob\n");
exit_status = 1;
goto END;
}
scanf(" %39s%*[^\n]", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
trans = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);

pda = m;
pdb = n;
pdd = m;
pde = n;
#ifdef NAG_COLUMN_MAJOR
pdc = m;
pdf = m;
#else
pdc = n;
pdf = n;
#endif

/* Allocate memory */
if (!(a = NAG_ALLOC(m * m, double)) || !(b = NAG_ALLOC(n * n, double)) ||
!(c = NAG_ALLOC(m * n, double)) || !(d = NAG_ALLOC(m * m, double)) ||
!(e = NAG_ALLOC(n * n, double)) || !(f = NAG_ALLOC(m * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read A, B, D, E, C and F from data file */
for (i = 1; i <= m; ++i)
for (j = 1; j <= m; ++j)
scanf("%lf", &a[K(i, j, pda)]);
scanf("%*[^\n]");
for (i = 1; i <= n; ++i)
for (j = 1; j <= n; ++j)
scanf("%lf", &b[K(i, j, pdb)]);
scanf("%*[^\n]");
for (i = 1; i <= m; ++i)
for (j = 1; j <= m; ++j)
scanf("%lf", &d[K(i, j, pdd)]);
scanf("%*[^\n]");
for (i = 1; i <= n; ++i)
for (j = 1; j <= n; ++j)
scanf("%lf", &e[K(i, j, pde)]);
scanf("%*[^\n]");
for (i = 1; i <= m; ++i)
for (j = 1; j <= n; ++j)
scanf("%lf", &c[K(i, j, pdc)]);
scanf("%*[^\n]");
for (i = 1; i <= m; ++i)
for (j = 1; j <= n; ++j)
scanf("%lf", &f[K(i, j, pdf)]);
scanf("%*[^\n]");

/* Solve the Sylvester equations:
* A*R - L*B = scale*C
* D*R - L*E = scale*F
*                     for R and L using  nag_lapackeig_dtgsyl (f08yhc).
*/
nag_lapackeig_dtgsyl(order, trans, ijob, m, n, a, pda, b, pdb, c, pdc, d, pdd,
e, pde, f, pdf, &scale, &dif, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapackeig_dtgsyl (f08yhc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print the solution matrices R and L */
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, m,
n, c, pdc, "Solution matrix R", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
printf("\n");
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, m,
n, f, pdf, "Solution matrix L", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
printf("\nscale = %11.2e\n", scale);

if (ijob > 0 && scale > 0.0) {
printf("\ndif   = %11.2e\n\n", dif);
printf("This estimate of Dif((A,D),(B,E)) was computed based on the ");
if (ijob == 1 || ijob == 3) {
printf("Frobenius norm.\n");
} else {
printf("one norm.\n");
}
}

END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(c);
NAG_FREE(d);
NAG_FREE(e);
NAG_FREE(f);

return exit_status;
}
```