```/* nag_matop_dtfttp (f01vlc) Example Program.
*
* Copyright 2020 Numerical Algorithms Group.
*
* Mark 27.1, 2020.
*/

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

int main(void) {
/* Scalars */
Integer exit_status = 0, indent = 0, ncols = 80;
Integer i, j, k, lar1, lar2, lenap, lenar, n, pdar, q;
/* Arrays */
double *ap = 0, *ar = 0;
char nag_enum_transr[40], nag_enum_uplo[40], form[] = "%5.2f";
/* Nag Types */
Nag_OrderType order;
Nag_RFP_Store transr;
Nag_UploType uplo;
NagError fail;

#ifdef NAG_COLUMN_MAJOR
order = Nag_ColMajor;
#define AR(I, J) ar[J * pdar + I]
#define KU(I, J) (I + J * (J + 1) / 2)
#define KL(I, J) (J * (n - 1) - J * (J - 1) / 2 + I)
#else
order = Nag_RowMajor;
#define AR(I, J) ar[I * pdar + J]
#define KL(I, J) (J + I * (I + 1) / 2)
#define KU(I, J) (I * (n - 1) - I * (I - 1) / 2 + J)
#endif

INIT_FAIL(fail);

printf("nag_matop_dtfttp (f01vlc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);
scanf("%39s ", nag_enum_transr);
scanf("%39s  %*[^\n] ", nag_enum_uplo);
lenap = (n * (n + 1)) / 2;
lenar = lenap;
if (!(ap = NAG_ALLOC(lenap, double)) || !(ar = NAG_ALLOC(lenar, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Nag_RFP_Store */
transr = (Nag_RFP_Store)nag_enum_name_to_value(nag_enum_transr);
uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_uplo);

k = n / 2;
q = n - k;
if (transr == Nag_RFP_Normal) {
lar1 = 2 * k + 1;
lar2 = q;
} else {
lar1 = q;
lar2 = 2 * k + 1;
}
if (order == Nag_RowMajor) {
pdar = lar2;
} else {
pdar = lar1;
}
/* Read an RFP matrix into array AR. */
for (i = 0; i < lar1; i++) {
for (j = 0; j < lar2; j++)
scanf("%lf ", &AR(i, j));
}

/* Print the Rectangular Full Packed array
* showing how the elements are arranged using
* nag_file_print_matrix_real_gen_comp (x04cbc).
* Print real general matrix (comprehensive).
*/
fflush(stdout);
nag_file_print_matrix_real_gen_comp(
order, Nag_GeneralMatrix, Nag_NonUnitDiag, lar1, lar2, ar, pdar, form,
"RFP Packed Array AR (graphical representation):", Nag_IntegerLabels,
NULL, Nag_IntegerLabels, NULL, ncols, indent, NULL, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen_comp (x04cbc).\n%s\n",
fail.message);
exit_status = 1;
}

/* Convert real triangular matrix from Rectangular Full Packed to
* packed vector form using nag_matop_dtfttp (f01vlc).
*/
nag_matop_dtfttp(order, transr, uplo, n, ar, ap, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_matop_dtfttp (f01vlc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print the packed vector using macros KL or KU. */
printf("\n Packed Matrix AP (printed using KL/KU macros):\n\n");
for (i = 0; i < n; i++) {
printf("  ");
if (uplo == Nag_Upper) {
for (j = 0; j < i; j++)
printf("%6s", " ");
for (j = i; j < n; j++)
printf("%6.2f", ap[KU(i, j)]);
} else {
for (j = 0; j <= i; j++)
printf("%6.2f", ap[KL(i, j)]);
}
printf("\n");
}

END:
NAG_FREE(ap);
NAG_FREE(ar);
return exit_status;
}
```