NAG Library Manual, Mark 28.3
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_specfun_bessel_i1_real_vector (s18atc) Example Program.
 *
 * Copyright 2022 Numerical Algorithms Group.
 *
 * Mark 28.3, 2022.
 */
#include <nag.h>
#include <stdio.h>

int main(void) {
  Integer exit_status = 0;
  Integer i, n;
  double *f = 0, *x = 0;
  Integer *ivalid = 0;
  NagError fail;

  INIT_FAIL(fail);

  /* Skip heading in data file */
  scanf("%*[^\n]");

  printf(
      "nag_specfun_bessel_i1_real_vector (s18atc) Example Program Results\n");
  printf("\n");
  printf("     x           f          ivalid\n");
  printf("\n");
  scanf("%" NAG_IFMT "", &n);
  scanf("%*[^\n]");

  /* Allocate memory */
  if (!(x = NAG_ALLOC(n, double)) || !(f = NAG_ALLOC(n, double)) ||
      !(ivalid = NAG_ALLOC(n, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

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

  /* nag_specfun_bessel_i1_real_vector (s18atc).
   * modified Bessel Function I1(x)
   */
  nag_specfun_bessel_i1_real_vector(n, x, f, ivalid, &fail);
  if (fail.code != NE_NOERROR && fail.code != NW_IVALID) {
    printf("Error from nag_specfun_bessel_i1_real_vector (s18atc).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

  for (i = 0; i < n; i++)
    printf(" %11.3e %11.3e %4" NAG_IFMT "\n", x[i], f[i], ivalid[i]);

END:
  NAG_FREE(f);
  NAG_FREE(x);
  NAG_FREE(ivalid);

  return exit_status;
}