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NAME
       y0, y1, yn - Bessel functions of the second kind


SYNOPSIS
       #include <math.h>

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


DESCRIPTION
       The y0(), y1(), and yn() functions shall compute Bessel functions of x of the second kind of orders 0, 1,
       and n, respectively.

       An  application  wishing  to  check  for  error  situations  should  set   errno   to   zero   and   call
       feclearexcept(FE_ALL_EXCEPT)  before  calling  these  functions.   On  return,  if  errno  is non-zero or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.


RETURN VALUE
       Upon successful completion, these functions shall return the relevant Bessel value of  x  of  the  second
       kind.

       If x is NaN, NaN shall be returned.

       If  the x argument to these functions is negative, -HUGE_VAL or NaN shall be returned, and a domain error
       may occur.

       If x is 0.0, -HUGE_VAL shall be returned and a range error may occur.

       If the correct result would cause underflow, 0.0 shall be returned and a range error may occur.

       If the correct result would cause overflow, -HUGE_VAL or 0.0 shall be returned  and  a  range  error  may
       occur.


ERRORS
       These functions may fail if:

       Domain Error
              The value of x is negative.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM].
       If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,  then  the  invalid  floating-
       point exception shall be raised.

       Range Error
              The value of x is 0.0, or the correct result would cause overflow.

       If  the  integer  expression  (math_errhandling  &  MATH_ERRNO)  is  non-zero, then errno shall be set to
       [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,  then  the  overflow
       floating-point exception shall be raised.

       Range Error
              The value of x is too large in magnitude, or the correct result would cause underflow.

       If  the  integer  expression  (math_errhandling  &  MATH_ERRNO)  is  non-zero, then errno shall be set to
       [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then  the  underflow
       floating-point exception shall be raised.

       The following sections are informative.


EXAMPLES
       None.


APPLICATION USAGE
       On  error,  the  expressions  (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are
       independent of each other, but at least one of them must be non-zero.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       feclearexcept() , fetestexcept() , isnan() , j0() , the Base Definitions volume of  IEEE Std 1003.1-2001,
       Section 4.18, Treatment of Error Conditions for Mathematical Functions, <math.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .