1J0(P)                      POSIX Programmer's Manual                     J0(P)
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NAME

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

9       #include <math.h>
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11       double j0(double x);
12       double j1(double x);
13       double jn(int n, double x);
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DESCRIPTION

17       The  j0(), j1(), and jn() functions shall compute Bessel functions of x
18       of the first kind of orders 0, 1, and n, respectively.
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20       An application wishing to check for error situations should  set  errno
21       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
22       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
23       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24       occurred.
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RETURN VALUE

27       Upon successful completion, these functions shall return  the  relevant
28       Bessel value of x of the first kind.
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30       If  the  x  argument  is  too large in magnitude, or the correct result
31       would cause underflow, 0 shall be returned and a range error may occur.
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33       If x is NaN, a NaN shall be returned.
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ERRORS

36       These functions may fail if:
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38       Range Error
39              The value of x was too  large  in  magnitude,  or  an  underflow
40              occurred.
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42       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
43       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
44       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow
45       floating-point exception shall be raised.
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48       No other errors shall occur.
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50       The following sections are informative.
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EXAMPLES

53       None.
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APPLICATION USAGE

56       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
57       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
58       at least one of them must be non-zero.
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RATIONALE

61       None.
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FUTURE DIRECTIONS

64       None.
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SEE ALSO

67       feclearexcept() , fetestexcept() , isnan() , y0() ,  the  Base  Defini‐
68       tions  volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
69       Conditions for Mathematical Functions, <math.h>
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72       Portions of this text are reprinted and reproduced in  electronic  form
73       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
74       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
75       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
76       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
77       event of any discrepancy between this version and the original IEEE and
78       The Open Group Standard, the original IEEE and The Open Group  Standard
79       is  the  referee document. The original Standard can be obtained online
80       at http://www.opengroup.org/unix/online.html .
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84IEEE/The Open Group                  2003                                J0(P)
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