lgamma-lgammaf-lgammal.md

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lgamma, lgammaf, lgammal	API reference for lgamma, lgammaf, and lgammal; which determines the natural logarithm of the absolute value of the gamma function of the specified value.	9/1/2020	lgamma lgammaf lgammal _o_lgamma _o_lgammaf _o_lgammal	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll api-ms-win-crt-math-l1-1-0.dll	DLLExport	apiref	lgamma lgammaf lgammal math/lgamma math/lgammaf math/lgammal	lgamma function lgammal function lgammaf function	6e326c58-7077-481a-a329-c82ae56ae9e6

lgamma, lgammaf, lgammal

Determines the natural logarithm of the absolute value of the gamma function of the specified value.

Syntax

double lgamma( double x );
float lgammaf( float x );
long double lgammal( long double x );
#define lgammal(X) // Requires C11 or higher

float lgamma( float x ); //C++ only
long double lgamma( long double x ); //C++ only

Parameters

x
The value to compute.

Return value

If successful, return the natural logarithm of the absolute value of the gamma function of x.

Issue	Return
x = NaN	NaN
x = ±0	+INFINITY
x= negative integer	+INFINITY
±INFINITY	+INFINITY
pole error	+HUGE_VAL, +HUGE_VALF, or +HUGE_VALL
overflow range error	±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL

Errors are reported as specified in _matherr.

Remarks

Because C++ allows overloading, you can call overloads of lgamma that take and return float and long double types. In a C program, unless you're using the <tgmath.h> macro to call this function, lgamma always takes and returns a double.

If you use the <tgmath.h> lgamma() macro, the type of the argument determines which version of the function is selected. See Type-generic math for details.

If x is a rational number, this function returns the logarithm of the factorial of (x - 1).

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Function	C header	C++ header
lgamma, lgammaf, lgammal	<math.h>	<cmath>
lgamma macro	<tgmath.h>

For more compatibility information, see Compatibility.

See also

Alphabetical function reference
tgamma, tgammaf, tgammal