1.4 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,

J0(5) = -1.775967713143382920e-01

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