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

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## 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`

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## 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.`

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`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.`

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## RETURN VALUE

33`Upon successful completion, these functions shall return the relevant`

34`Bessel value of x of the second kind.`

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`If x is NaN, NaN shall be returned.`

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`If the x argument to these functions is negative, -HUGE_VAL or NaN`

39`shall be returned, and a domain error may occur.`

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`If x is 0.0, -HUGE_VAL shall be returned and a range error may occur.`

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`If the correct result would cause underflow, 0.0 shall be returned and`

44`a range error may occur.`

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`If the correct result would cause overflow, -HUGE_VAL or 0.0 shall be`

47`returned and a range error may occur.`

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## ERRORS

50`These functions may fail if:`

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`Domain Error`

53`The value of x is negative.`

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`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.`

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`Range Error`

61`The value of x is 0.0, or the correct result would cause over‐`

62`flow.`

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`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.`

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`Range Error`

70`The value of x is too large in magnitude, or the correct result`

71`would cause underflow.`

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`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.`

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`The following sections are informative.`

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## EXAMPLES

82`None.`

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## 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.`

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## RATIONALE

90`None.`

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## FUTURE DIRECTIONS

93`None.`

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## SEE ALSO

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>`

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## COPYRIGHT

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 .`

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`IEEE/The Open Group 2003 Y0(3P)`