Y0(3) Linux Programmer's Manual Y0(3)
y0, y0f, y0l, y1, y1f, y1l, yn, ynf, ynl - Bessel functions of the second kind
double y0(double x);
double y1(double x);
double yn(int n, double x);
float y0f(float x);
float y1f(float x);
float ynf(int n, float x);
long double y0l(long double x);
long double y1l(long double x);
long double ynl(int n, long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
y0(), y1(), yn():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE
y0f(), y0l(), y1f(), y1l(), ynf(), ynl():
_SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600
The y0() and y1() functions return Bessel functions of x of the second kind of orders 0
and 1, respectively. The yn() function returns the Bessel function of x of the second
kind of order n.
The value of x must be positive.
The y0f() etc. and y0l() etc. functions are versions that take and return float and long
double values, respectively.
On success, these functions return the appropriate Bessel value of the second kind for x.
If x is a NaN, a NaN is returned.
If x is negative, a domain error occurs, and the functions return -HUGE_VAL, -HUGE_VALF,
or -HUGE_VALL, respectively. (POSIX.1-2001 also allows a NaN return for this case.)
If x is 0.0, a pole error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or
If the result underflows, a range error occurs, and the functions return 0.0
If the result overflows, a range error occurs, and the functions return -HUGE_VAL,
-HUGE_VALF, or -HUGE_VALL, respectively. (POSIX.1-2001 also allows a 0.0 return for this
See math_error(7) for information on how to determine whether an error has occurred when
calling these functions.
The following errors can occur:
Domain error: x is negative
errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.
Pole error: x is 0.0
errno is set to ERANGE (but see BUGS). No FE_DIVBYZERO exception is returned by
fetestexcept(3) for this case.
Range error: result underflow
errno is set to ERANGE. No FE_UNDERFLOW exception is returned by fetestexcept(3)
for this case.
Range error: result overflow
errno is not set for this case. An overflow floating-point exception (FE_OVERFLOW)
The functions returning double conform to SVr4, 4.3BSD, POSIX.1-2001. The others are non-
standard functions that also exist on the BSDs.
On a pole error, these functions set errno to EDOM, instead of ERANGE as POSIX.1-2004
In glibc version 2.3.2 and earlier, these functions do not raise an invalid floating-point
exception (FE_INVALID) when a domain error occurs.
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