posix man page for y1

Y0(P)							     POSIX Programmer's Manual							     Y0(P)

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>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								     Y0(P)