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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 dif-
       fer (consult 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,
       respectively.

       An application  wishing  to  check  for  error  situations  should  set  errno  to  zero  and  call  feclearex-
       cept(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 indepen-
       dent 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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(3P)