y1(), y1f()

Updated: May 06, 2022

Compute a Bessel function of the second kind of order 1

Synopsis:

#include <math.h>

double y1( double x );

float y1f( float x );

Arguments:

x
The number that you want to compute the Bessel function for.

Library:

libm
The general-purpose math library.
libm-sve
(QNX Neutrino 7.1 or later) 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:

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 second kind of order 1.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Returns:

The result of the Bessel function for x of second kind of order 1.

If x is: These functions return: Errors:
Negative, including -Inf NaN FE_INVALID
±0.0 -Inf FE_DIVBYZERO
NaN NaN
Inf 0.0
If the correct result would cause: These functions return: Errors:
Overflow -Inf FE_OVERFLOW
Underflow 0.0  

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

Examples:

#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
{
    int except_flags;
    double x, y, z;

    feclearexcept(FE_ALL_EXCEPT);

    x = j0( 2.4 );

    except_flags = fetestexcept(FE_ALL_EXCEPT);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    feclearexcept(FE_ALL_EXCEPT);

    y = y1( 1.58 );

    except_flags = fetestexcept(FE_ALL_EXCEPT);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    feclearexcept(FE_ALL_EXCEPT);

    z = jn( 3, 2.4 );

    except_flags = fetestexcept(FE_ALL_EXCEPT);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    printf( "j0(2.4) = %f, y1(1.58) = %f\n", x, y );
    printf( "jn(3,2.4) = %f\n", z );

    return EXIT_SUCCESS;
}

Classification:

y1() is POSIX 1003.1 XSI; y1f() is Unix

Safety:  
Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes