IEEE Std 1003.1-2008

Copyright © 2001-2008 The IEEE and The Open Group

y0, y1, yn - Bessel functions of the second kind

^{[XSI]}#include <math.h>

double y0(doublex);

double y1(doublex);

double yn(intn, doublex);

The

y0(),y1(), andyn() functions shall compute Bessel functions ofxof the second kind of orders 0, 1, andn, respectively.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(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

xof the second kind.If

xis NaN, NaN shall be returned.If the

xargument to these functions is negative, -HUGE_VAL or NaN shall be returned, and a domain error may occur.If

xis 0.0, -HUGE_VAL shall be returned and a pole error may occur.If the correct result would cause underflow, 0.0 shall be returned and a range error may occur.

If the correct result would cause overflow, -HUGE_VAL or 0.0 shall be returned and a range error may occur.

These functions may fail if:

- Domain Error
- The value of
xis negative.If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [EDOM]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.- Pole Error
- The value of
xis zero.If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.- Range Error
- The correct result would cause overflow.
If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.- Range Error
- The value of
xis too large in magnitude, or the correct result would cause underflow.If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

None.

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.

None.

None.

feclearexcept,fetestexcept,isnan,j0XBD

Treatment of Error Conditions for Mathematical Functions,<math.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

The normative text is updated to avoid use of the term "must" for application requirements.

The RETURN VALUE and ERRORS sections are reworked for alignment of the error handling with the ISO/IEC 9899:1999 standard.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/148 is applied, updating the RETURN VALUE and ERRORS sections. The changes are made for consistency with the general rules stated in "Treatment of Error Conditions for Mathematical Functions'' in the Base Definitions volume of POSIX.1-2008.

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