lgammal(3p) [centos man page]

```LGAMMA(3P)						     POSIX Programmer's Manual							LGAMMA(3P)

PROLOG
This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME
lgamma, lgammaf, lgammal - log gamma function

SYNOPSIS
#include <math.h>

double lgamma(double x);
float lgammaf(float x);
long double lgammal(long double x);

extern int signgam;

DESCRIPTION
These functions shall compute

The argument x need not be a non-positive integer (Gamma(x) is defined over the reals, except the non-positive integers).

The sign of Gamma(x) is returned in the external integer signgam.

These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
has occurred.

RETURN VALUE
Upon successful completion, these functions shall return the logarithmic gamma of x.

If x is a non-positive integer, a pole error shall occur and lgamma(), lgammaf(), and lgammal() shall  return  +HUGE_VAL,  +HUGE_VALF,  and
+HUGE_VALL, respectively.

If  the	correct  value	would  cause  overflow,  a range error shall occur and lgamma(), lgammaf(), and lgammal() shall return +-HUGE_VAL,
+-HUGE_VALF, and +-HUGE_VALL (having the same sign as the correct value), respectively.

If x is NaN, a NaN shall be returned.

If x is 1 or 2, +0 shall be returned.

If x is +-Inf, +Inf shall be returned.

ERRORS
These functions shall fail if:

Pole Error
The x argument is a negative integer or zero.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall 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 result overflows.

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

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
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.

RATIONALE
None.

FUTURE DIRECTIONS
None.

exp(), feclearexcept(), fetestexcept(), isnan(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Con-
ditions for Mathematical Functions, <math.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .

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

Check Out this Related Man Page

```LGAMMA(3P)						     POSIX Programmer's Manual							LGAMMA(3P)

PROLOG
This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME
lgamma, lgammaf, lgammal - log gamma function

SYNOPSIS
#include <math.h>

double lgamma(double x);
float lgammaf(float x);
long double lgammal(long double x);

extern int signgam;

DESCRIPTION
These functions shall compute

The argument x need not be a non-positive integer (Gamma(x) is defined over the reals, except the non-positive integers).

The sign of Gamma(x) is returned in the external integer signgam.

These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
has occurred.

RETURN VALUE
Upon successful completion, these functions shall return the logarithmic gamma of x.

If x is a non-positive integer, a pole error shall occur and lgamma(), lgammaf(), and lgammal() shall  return  +HUGE_VAL,  +HUGE_VALF,  and
+HUGE_VALL, respectively.

If  the	correct  value	would  cause  overflow,  a range error shall occur and lgamma(), lgammaf(), and lgammal() shall return +-HUGE_VAL,
+-HUGE_VALF, and +-HUGE_VALL (having the same sign as the correct value), respectively.

If x is NaN, a NaN shall be returned.

If x is 1 or 2, +0 shall be returned.

If x is +-Inf, +Inf shall be returned.

ERRORS
These functions shall fail if:

Pole Error
The x argument is a negative integer or zero.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall 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 result overflows.

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

The following sections are informative.

EXAMPLES
None.

APPLICATION USAGE
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.

RATIONALE
None.

FUTURE DIRECTIONS
None.

exp(), feclearexcept(), fetestexcept(), isnan(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Con-
ditions for Mathematical Functions, <math.h>