# y1l

```       ond 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);

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
Pole error: x is 0.0
errno is set to ERANGE (but see BUGS).  No  FE_DIVBYZERO  excep-
tion 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.