j0, j1, jn, y0, y1, yn - bessel functions

 #include <math.h> 

 double j0(x)  double x; 

 double j1(x)  double x; 

 double jn(n,x)  int n;  double x; 

 double y0(x)  double x; 

 double y1(x)  double x; 

 double yn(n,x)  int n;  double x; 

These functions calculate Bessel functions of the first and second kinds for real arguments and integer orders. intro(3M), infnan(3M) On a VAX, negative arguments cause y0, y1 and yn to return the reserved operand and set errno to EDOM.