J0(P)							     POSIX Programmer's Manual							     J0(P)

NAME

       j0, j1, jn - Bessel functions of the first kind

SYNOPSIS

       #include <math.h>

       double j0(double x);
       double j1(double x);
       double jn(int n, double x);

DESCRIPTION

       The j0(), j1(), and jn() functions shall compute Bessel functions of x of the first 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 first kind.

       If the x argument is too large in magnitude, or the correct result would cause underflow, 0 shall be returned and a range error may occur.

       If x is NaN, a NaN shall be returned.

ERRORS

       These functions may fail if:

       Range Error
	      The value of x was too large in magnitude, or an underflow occurred.

       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.

       No other errors shall occur.

       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() , y0() , 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								     J0(P)