NAG Library Manual, Mark 28.5
```/* nag_matop_dtfttr (f01vgc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/

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

int main(void) {
/* Scalars */
Integer exit_status = 0, indent = 0, ncols = 80;
Integer i, j, k, lar1, lar2, lenar, pda, pdar, q, n;
/* Arrays */
double *a = 0, *ar = 0;
char nag_enum_transr[40], nag_enum_uplo[40], form[] = "%5.2f";
/* Nag Types */
Nag_MatrixType matrix;
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]
#else
order = Nag_RowMajor;
#define AR(I, J) ar[I * pdar + J]
#endif

INIT_FAIL(fail);

printf("nag_matop_dtfttr (f01vgc) 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);
pda = n;
lenar = (n * (n + 1)) / 2;
if (!(a = NAG_ALLOC(pda * n, double)) || !(ar = NAG_ALLOC(lenar, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
transr = (Nag_RFP_Store)nag_enum_name_to_value(nag_enum_transr);
uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_uplo);

/* Read an RFP matrix into array ar. */
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;
}
printf("\n");

/* Copy real triangular matrix from Rectangular Full Packed format, ar,
* to full format a using nag_matop_dtfttr (f01vgc).
*/
nag_matop_dtfttr(order, transr, uplo, n, ar, a, pda, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_matop_dtfttr (f01vgc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print the unpacked array. */
matrix = (uplo == Nag_Upper ? Nag_UpperMatrix : Nag_LowerMatrix);

/* nag_file_print_matrix_real_gen_comp (x04cbc).
* Print real general matrix (comprehensive).
*/
fflush(stdout);
nag_file_print_matrix_real_gen_comp(
order, matrix, Nag_NonUnitDiag, n, n, a, pda, form,
"Unpacked Matrix A:", 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;
}

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