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NAME

       y0, y0f, y0l, y1, y1f, y1l, yn, ynf, ynl - Bessel functions of the second kind

SYNOPSIS

       #include <math.h>

       double y0(double x);
       double y1(double x);
       double yn(int n, double x);

       float y0f(float x);
       float y1f(float x);
       float ynf(int n, float x);

       long double y0l(long double x);
       long double y1l(long double x);
       long double ynl(int n, long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       y0(), y1(), yn():
           _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE
       y0f(), y0l(), y1f(), y1l(), ynf(), ynl():
           _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600

DESCRIPTION

       The  y0()  and  y1() functions return Bessel functions of x of the second kind of orders 0
       and 1, respectively.  The yn() function returns the Bessel function of  x  of  the  second
       kind of order n.

       The value of x must be positive.

       The  y0f()  etc. and y0l() etc. functions are versions that take and return float and long
       double values, respectively.

RETURN VALUE

       On success, these functions return the appropriate Bessel value of the second kind for x.

       If x is a NaN, a NaN is returned.

       If x is negative, a domain error occurs, and the functions return  -HUGE_VAL,  -HUGE_VALF,
       or -HUGE_VALL, respectively.  (POSIX.1-2001 also allows a NaN return for this case.)

       If  x  is  0.0,  a  pole  error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or
       -HUGE_VALL, respectively.

       If the result underflows, a range error occurs, and the functions return 0.0

       If the result overflows, a  range  error  occurs,  and  the  functions  return  -HUGE_VAL,
       -HUGE_VALF,  or -HUGE_VALL, respectively.  (POSIX.1-2001 also allows a 0.0 return for this
       case.)

ERRORS

       See math_error(7) for information on how to determine whether an error has  occurred  when
       calling these functions.

       The following errors can occur:

       Domain error: x is negative
              errno is set to EDOM.  An invalid floating-point exception (FE_INVALID) is raised.

       Pole error: x is 0.0
              errno  is  set  to ERANGE (but see BUGS).  No FE_DIVBYZERO exception is returned by
              fetestexcept(3) for this case.

       Range error: result underflow
              errno is set to ERANGE.  No FE_UNDERFLOW exception is returned  by  fetestexcept(3)
              for this case.

       Range error: result overflow
              errno is not set for this case.  An overflow floating-point exception (FE_OVERFLOW)
              is raised.

CONFORMING TO

       The functions returning double conform to SVr4,  4.3BSD,  POSIX.1-2001.   The  others  are
       nonstandard functions that also exist on the BSDs.

BUGS

       On  a  pole  error,  these  functions set errno to EDOM, instead of ERANGE as POSIX.1-2004
       requires.

       In glibc version 2.3.2 and earlier, these functions do not raise an invalid floating-point
       exception (FE_INVALID) when a domain error occurs.

SEE ALSO

       j0(3)

COLOPHON

       This  page  is  part of release 3.35 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.

                                            2008-08-10                                      Y0(3)