1J0(3P)                     POSIX Programmer's Manual                    J0(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       j0, j1, jn — Bessel functions of the first kind
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SYNOPSIS

16       #include <math.h>
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18       double j0(double x);
19       double j1(double x);
20       double jn(int n, double x);
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DESCRIPTION

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

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

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

58       None.
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APPLICATION USAGE

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

66       None.
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FUTURE DIRECTIONS

69       None.
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SEE ALSO

72       feclearexcept(), fetestexcept(), isnan(), y0()
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74       The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
75       Error Conditions for Mathematical Functions, <math.h>
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78       Portions  of  this text are reprinted and reproduced in electronic form
79       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
80       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
81       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
82       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
83       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
84       event of any discrepancy between this version and the original IEEE and
85       The Open Group Standard, the original IEEE and The Open Group  Standard
86       is  the  referee document. The original Standard can be obtained online
87       at http://www.unix.org/online.html .
88
89       Any typographical or formatting errors that appear  in  this  page  are
90       most likely to have been introduced during the conversion of the source
91       files to man page format. To report such errors,  see  https://www.ker‐
92       nel.org/doc/man-pages/reporting_bugs.html .
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96IEEE/The Open Group                  2013                               J0(3P)
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