J0(3P)                                              POSIX Programmer's Manual                                             J0(3P)



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

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, respec-
       tively.

       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 inte-
       ger 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, Treat-
       ment 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 Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                        J0(3P)