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2.1 An Example Program

The following short program demonstrates the use of the library by computing the value of the Bessel function J_0(x) for 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,2

J0(5) = -1.775967713143382920e-01

The steps needed to compile this program are described in the following sections.


Footnotes

(2)

The last few digits may vary slightly depending on the compiler and platform used—this is normal.