//  file: j0_test.cpp
//
//  C++ Program to demonstrate use of the J0 Bessel function from
//   the gsl numerical library.
//
//  Programmer:  Dick Furnstahl  furnstahl.1@osu.edu
//
//  Revision history:
//      12/26/03  original C++ version, modified from C version
//
//  Notes:  
//   * Example taken from the GNU Scientific Library Reference Manual
//      Edition 1.1, for GSL Version 1.1 9 January 2002
//      URL: gsl/ref/gsl-ref_23.html#SEC364
//   * Compile and link with:
//       g++ -Wall -o J0_test J0_test.cpp -lgsl -lgslcblas
//   * gsl routines have built-in 
//       extern "C" {
//          <header stuff>
//       }
//      so they can be called from C++ programs without modification
//   * The answer should be J0(5) = -1.775967713143382920e-01 
//
//*********************************************************************//

// include files
#include <iostream>
#include <iomanip>
#include <fstream>
#include <math.h>
using namespace std;

#include <gsl/gsl_sf_bessel.h>  // gsl Bessel special function header file


int
main (void)
{
  double x = 5.0;   // just a random test value

  double y = gsl_sf_bessel_J0 (x);   // see the GSL manual for details

  cout << "J0(" << x << ") = " 
       << setprecision(18) << setw(20) << y << endl;

  return 0;
}