NAG Library Manual, Mark 28.6
```/* nag_lapacklin_zptcon (f07juc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.6, 2022.
*
* UNFINISHED - replace commented out climp calls
*/

#include <math.h>
#include <nag.h>

int main(void) {
#define CABS(e) sqrt(e.re *e.re + e.im * e.im)

/* Scalars */
double anorm, rcond;
Integer exit_status = 0, i, n;

/* Arrays */
Complex *e = 0;
double *d = 0;

/* Nag Types */
NagError fail;

INIT_FAIL(fail);

printf("nag_lapacklin_zptcon (f07juc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%*[^\n]", &n);
if (n < 0) {
printf("Invalid n\n");
exit_status = 1;
goto END;
}

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

/* Read the lower bidiagonal part of the tridiagonal matrix A from */
/* data file */
for (i = 0; i < n; ++i)
scanf("%lf", &d[i]);
scanf("%*[^\n]");
for (i = 0; i < n - 1; ++i)
scanf(" ( %lf , %lf )", &e[i].re, &e[i].im);
scanf("%*[^\n]");

/* Compute the 1-norm of A */
anorm = MAX(ABS(d[0]) + CABS(e[0]), CABS(e[n - 2]) + ABS(d[n - 1]));
for (i = 1; i < n - 1; ++i)
anorm = MAX(anorm, ABS(d[i]) + CABS(e[i]) + CABS(e[i - 1]));

/* Factorize A using nag_lapacklin_zpttrf (f07jrc). */
nag_lapacklin_zpttrf(n, d, e, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_zpttrf (f07jrc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Estimate the condition number of A using nag_lapacklin_zptcon (f07juc). */
nag_lapacklin_zptcon(n, d, e, anorm, &rcond, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_zptcon (f07juc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print the estimated condition number */
if (rcond >= nag_machine_precision)
printf("Estimate of condition number = %11.2e\n\n", 1.0 / rcond);
else
printf("A is singular to working precision. RCOND = %11.2e\n\n", rcond);

END:
NAG_FREE(e);
NAG_FREE(d);

return exit_status;
}
```