trusty (3) j1.3posix.gz

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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>


       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 .