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

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

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

#include <math.h>
double j0(double x);
double j1(double x);
double jn(int n, double x);

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.

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.

These functions may fail if:

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.


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.



feclearexcept(), fetestexcept(), isnan(), y0()

The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

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2017 IEEE/The Open Group