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

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

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

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

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

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

57       None.
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APPLICATION USAGE

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

65       None.
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FUTURE DIRECTIONS

68       None.
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SEE ALSO

71       feclearexcept(), fetestexcept(), isnan(), y0()
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73       The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
74       Error Conditions for Mathematical Functions, <math.h>
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77       Portions  of  this text are reprinted and reproduced in electronic form
78       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
79       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
80       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
81       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
82       event of any discrepancy between this version and the original IEEE and
83       The  Open Group Standard, the original IEEE and The Open Group Standard
84       is the referee document. The original Standard can be  obtained  online
85       at http://www.opengroup.org/unix/online.html .
86
87       Any  typographical  or  formatting  errors that appear in this page are
88       most likely to have been introduced during the conversion of the source
89       files  to  man page format. To report such errors, see https://www.ker‐
90       nel.org/doc/man-pages/reporting_bugs.html .
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94IEEE/The Open Group                  2017                               J0(3P)
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