/* nag_example_file_io (x04aec) Example Program.
 *
 * Copyright 2011, Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nage01.h>
#include <nagx04.h>

int main(int argc, char *argv[])
{
  /* Scalars */
  FILE    *fpin = 0, *fpout = 0;
  Integer exit_status = 0;
  Integer i, j, k, n;
  double  x;
  NagError fail;
  /* Arrays */
  double  *a = 0, *b = 0, *c = 0;

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fpin = nag_example_file_io(argc, argv, "-data", NULL);
  fprintf(fpout, "nag_example_file_io (x04aec) Example Program Results\n");

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

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

  for (i = 0; i < n + 1; i++){
    fscanf(fpin, "%lf", &a[i]);
  }
  fscanf(fpin, "%*[^\n] ");
  for (i = 0; i < n + 1; i++){
    fscanf(fpin, "%lf", &b[i]);
  }
  fscanf(fpin, "%*[^\n] ");

  /* nag_1d_aitken_interp (e01aac).
   * Interpolated values, Aitken's technique,
   * unequally spaced data, one variable.
   */
  nag_1d_aitken_interp(n, a, b, c, x, &fail);
  if (fail.code != NE_NOERROR){
    fprintf(fpout, "Error from nag_1d_aitken_interp (e01aac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

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

 END:
  if (fpin != stdin) fclose(fpin);
  if (fpout != stdout) fclose(fpout);
  if (a) NAG_FREE(a);
  if (b) NAG_FREE(b);
  if (c) NAG_FREE(c);

  return exit_status;
}