/* nag_interp_dim1_aitken (e01aac) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer exit_status = 0;
  Integer i, j, k, n;
  double x;
  NagError fail;
  /* Arrays */
  double *a = 0, *b = 0, *c = 0;

  INIT_FAIL(fail);

  printf("nag_interp_dim1_aitken (e01aac) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "", &n);
  scanf("%lf", &x);
  scanf("%*[^\n] ");

  /* Allocate memory */
  if (!(a = NAG_ALLOC((n + 1), double)) || !(b = NAG_ALLOC((n + 1), double)) ||
      !(c = NAG_ALLOC((n * (n + 1) / 2), double))) {
    printf("Allocation failure\n\n");
    exit_status = -1;
    goto END;
  }

  for (i = 0; i <= n; i++)
    scanf("%lf", &a[i]);
  scanf("%*[^\n] ");
  for (i = 0; i <= n; i++)
    scanf("%lf", &b[i]);
  scanf("%*[^\n] ");

  /* nag_interp_dim1_aitken (e01aac).
   * Interpolated values, Aitken's technique,
   * unequally spaced data, one variable.
   */
  nag_interp_dim1_aitken(n, a, b, c, x, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_interp_dim1_aitken (e01aac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  printf("Interpolated values\n");
  k = 0;
  for (i = 1; i <= n - 1; i++) {
    for (j = k; j <= k + n - i; j++)
      printf("%12.5f", c[j]);
    printf("\n");
    k = j;
  }
  printf("\nInterpolation point = %12.5f\n", x);
  printf("\nFunction value at interpolation point = %12.5f\n",
         c[n * (n + 1) / 2 - 1]);

END:
  NAG_FREE(a);
  NAG_FREE(b);
  NAG_FREE(c);

  return exit_status;
}