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Y0(3P)                     POSIX Programmer's Manual                    Y0(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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  over-
              flow.
       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 Condi-
       tions 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 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 .

IEEE/The Open Group                  2003                               Y0(3P)