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lgammad64.3m (2010 09)

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lgammad64(3M) lgammad64(3M)
(HP Integrity Server Only)
NAME
lgammad64(), lgammad128(), lgammad32() - decimal log gamma functions
SYNOPSIS
#define __STDC_WANT_DEC_FP__
#include <math.h>
_Decimal64 lgammad64(_Decimal64 x);
_Decimal128 lgammad128(_Decimal128 x);
_Decimal32 lgammad32(_Decimal32 x);
DESCRIPTION
lgammad64() returns log(|Γ(x)|), where Γ(x) is defined as the integral, as t goes from zero to
infinity, of
exp(−t
) times t to the power (x−1).
The sign of Γ(x) is returned in the external integer
signgam.
lgammad64() is not reentrant because it uses the global variable
signgam.
The
tgammad64() function can be used to calculate Γ(x).
lgammad128() is a _Decimal128 version of lgammad64(); it takes a _Decimal128 argument and
returns a _Decimal128 result.
lgammad32() is a _Decimal32 version of lgammad64(); it takes a _Decimal32 argument and
returns a _Decimal32 result.
These math functions are supported for HP-UX 11i Version 3 September 2008 Update and forward.
USAGE
To use any of these functions, compile with the +decfp option.
Make sure your program defines
__STDC_WANT_DEC_FP__
and then includes <math.h>.
Link in the math library by specifying
-lm or -l:libm.a on the linking command line.
For more information, see the HP-UX floating-point guide for HP Integrity servers at the following site:
http://www.hp.com/go/fp
.
RETURN VALUE
lgammad64(1) returns +0.
lgammad64(2) returns +0.
lgammad64(x) returns +infinity and raises the divide-by-zero floating-point exception for x anegative
integer or zero.
If x is ±infinity,
lgammad64() returns +infinity.
If x is NaN,
lgammad64() returns NaN.
lgammad64() returns +infinity (or, in some non-default rounding direction modes, the maximum finite
number) in lieu of a value whose magnitude is too large, and raises the overflow and inexact exceptions.
lgammad64() raises the inexact exception whenever a rounded result does not equal the mathematical
result.
ERRORS
If x is a negative integer or zero,
lgammad64() sets errno to [ERANGE].
If the correct value would overflow,
lgammad64() sets errno to [ERANGE].
SEE ALSO
expd64(3M), logd64(3M), tgammad64(3M), math(5).
STANDARDS CONFORMANCE
These functions conform to ISO/IEC TR 24732, "Extension for the programming language C to support
decimal floating-point arithmetic".
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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