```1`Y0(3P)                     POSIX Programmer's Manual                    Y0(3P)`
2
3
4
```

## PROLOG

```6`       This  manual  page is part of the POSIX Programmer's Manual.  The Linux`
7`       implementation of this interface may differ (consult the  corresponding`
8`       Linux  manual page for details of Linux behavior), or the interface may`
9`       not be implemented on Linux.`
10
```

## NAME

```12`       y0, y1, yn - Bessel functions of the second kind`
13
```

## SYNOPSIS

```15`       #include <math.h>`
16
17`       double y0(double x);`
18`       double y1(double x);`
19`       double yn(int n, double x);`
20
21
```

## DESCRIPTION

```23`       The y0(), y1(), and yn() functions shall compute Bessel functions of  x`
24`       of the second kind of orders 0, 1, and n, respectively.`
25
26`       An  application  wishing to check for error situations should set errno`
27`       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these`
28`       functions.   On return, if errno is non-zero or fetestexcept(FE_INVALID`
29`       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has`
30`       occurred.`
31
```

## RETURN VALUE

```33`       Upon  successful  completion, these functions shall return the relevant`
34`       Bessel value of x of the second kind.`
35
36`       If x is NaN, NaN shall be returned.`
37
38`       If the x argument to these functions  is  negative,  -HUGE_VAL  or  NaN`
39`       shall be returned, and a domain error may occur.`
40
41`       If x is 0.0, -HUGE_VAL shall be returned and a range error may occur.`
42
43`       If  the correct result would cause underflow, 0.0 shall be returned and`
44`       a range error may occur.`
45
46`       If the correct result would cause overflow, -HUGE_VAL or 0.0  shall  be`
47`       returned and a range error may occur.`
48
```

## ERRORS

```50`       These functions may fail if:`
51
52`       Domain Error`
53`              The value of x is negative.`
54
55`       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,`
56`       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression`
57`       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid`
58`       floating-point exception shall be raised.`
59
60`       Range Error`
61`              The value of x is 0.0, or the correct result would  cause  over‐`
62`              flow.`
63
64`       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,`
65`       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression`
66`       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow`
67`       floating-point exception shall be raised.`
68
69`       Range Error`
70`              The value of x is too large in magnitude, or the correct  result`
71`              would cause underflow.`
72
73`       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,`
74`       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression`
75`       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow`
76`       floating-point exception shall be raised.`
77
78
79`       The following sections are informative.`
80
```

## EXAMPLES

```82`       None.`
83
```

## APPLICATION USAGE

```85`       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and`
86`       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but`
87`       at least one of them must be non-zero.`
88
```

## RATIONALE

```90`       None.`
91
```

## FUTURE DIRECTIONS

```93`       None.`
94
```

```96`       feclearexcept(), fetestexcept(), isnan(), j0(),  the  Base  Definitions`
97`       volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi‐`
98`       tions for Mathematical Functions, <math.h>`
99
```
```101`       Portions of this text are reprinted and reproduced in  electronic  form`
102`       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology`
103`       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base`
104`       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of`
105`       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the`
106`       event of any discrepancy between this version and the original IEEE and`
107`       The Open Group Standard, the original IEEE and The Open Group  Standard`
108`       is  the  referee document. The original Standard can be obtained online`
109`       at http://www.opengroup.org/unix/online.html .`
110
111
112
113`IEEE/The Open Group                  2003                               Y0(3P)`
```