An Example Program

The following short program demonstrates the use of the library by computing the value of the Bessel function @math{J_0(x)} for @math{x=5},

#include <stdio.h>
#include <gsl/gsl_sf_bessel.h>

int
main (void)
{
  double x = 5.0;

  double y = gsl_sf_bessel_J0 (x);

  printf("J0(%g) = %.18e\n", x, y);

  return 0;
}

The output is shown below, and should be correct to double-precision accuracy,

J0(5) = -1.775967713143382920e-01

The steps needed to compile programs which use the library are described in the next chapter.