j1(), j1f()
QNX SDP8.0C Library ReferenceAPIDeveloper
Compute a Bessel function of the first kind of order 1
Synopsis:
#include <math.h>
double j1( double x );
float j1f( float x );
Arguments:
- x
- The number that you want to compute the Bessel function for.
Library:
- libm
- The general-purpose math library.
- libm-sve
- A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.
Your system requirements will determine how you should work with these libraries:
- If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
- If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.
Note:
Compile your program with the -fno-builtin option to prevent the compiler from using a
built-in version of the function.
Description:
These functions compute the Bessel function for x of the first kind of order 1.
To check for error situations, use feclearexcept() and fetestexcept(). For example:
- Call
feclearexcept(FE_ALL_EXCEPT)before calling j1() or j1f(). - On return, if
fetestexcept(FE_ALL_EXCEPT)is nonzero, then an error has occurred.
Returns:
The Bessel value of x of the first kind of order 1.
| If: | These functions return: | Errors: |
|---|---|---|
| x is ±0.0 | 0.0, with the same sign as x | — |
| x is ±Inf | 0.0, with the same sign as x | — |
| x is NaN | NaNNaN | — |
| The correct result would cause underflow | 0.0 | FE_UNDERFLOW |
These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.
Classification:
j1() is POSIX 1003.1 XSI; j1f() is Unix
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
Page updated: