J0(3P)

💖 PROLOG 💖

okay so bestie, real talk before we get into it: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so go consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not even be implemented on Linux at all. 🙈

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✨ NAME ✨

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

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🦋 SYNOPSIS 🦋

#include <math.h>

double j0(double x);
double j1(double x);
double jn(int n, double x);

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🌸 DESCRIPTION 🌸

so the girlies j0(), j1(), and jn() shall compute Bessel functions of x of the first kind of orders 0, 1, and n, respectively. that's it, that's the job. 💅

Now if your application wants to check for error situations (and honestly, icon behavior), you should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. Then on return: if errno is non-zero, or if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. no cap. ⭐

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👑 RETURN VALUE 👑

Upon successful completion, these functions shall return the relevant Bessel value of x of the first kind. slay.

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.

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💀 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. periodt. 🫶

The following sections are informative — aka they're the vibe, not the rules. 🧚

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🍓 EXAMPLES 🍓

None. 💀 (not a single one. we move.)

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🌈 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. iykyk. 💜

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🎀 RATIONALE 🎀

None.

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⭐ FUTURE DIRECTIONS ⭐

None.

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🔥 SEE ALSO 🔥

• feclearexcept()
• fetestexcept()
• isnan()
• y0()

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

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💖 COPYRIGHT 💖

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 .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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okay bestie that's the whole page, mwah 🫶 this one came from IEEE/The Open Group, 2017 (the page is J0(3P), in case you forgot which girl we were talking about 💅). go forth and compute ur Bessel functions, main character. ✨