lgammad32(), lgammad64(), lgammad128()

Standards

Standards / Extensions	C or C++	Dependencies
C/C++ DFP	both	z/OS® V1.10

Format

#define __STDC_WANT_DEC_FP__
#include <math.h>

_Decimal32  lgammad32(_Decimal32 x);
_Decimal64  lgammad64(_Decimal64 x);
_Decimal128 lgammad128(_Decimal128 x);
_Decimal32  lgamma(_Decimal32 x);     /* C++ only */
_Decimal64  lgamma(_Decimal64 x);     /* C++ only */
_Decimal128 lgamma(_Decimal128 x);    /* C++ only */

General description

The lgamma() function computes the

is defined as

The sign of

is returned in the external integer signgam. The argument x may not be a non-positive integer.

In a multithreaded process, each thread has its own instance of the signgam variable. Threads access their instances of the variable by calling the __signgam() function. The math.h header redefines the string signgam to an invocation of the __siggam function. The actual signgam external variable is used to store the signgam value for the IPT.

These functions work in IEEE decimal floating-point format. See IEEE decimal floating-point for more information.

Note: To use IEEE decimal floating-point, the hardware must have the Decimal Floating-Point Facility installed.

Returned value

If successful, lgamma() returns the above function of its argument.

lgamma() will fail under the following conditions:

If the result overflows, the function will return +HUGE_VAL_D32, +HUGE_VAL_D64 or +HUGE_VAL_D128 and set errno to ERANGE.
If x is a non-positive integer, lgamma() returns +HUGE_VAL_D32, +HUGE_VAL_D64 or +HUGE_VAL_D128 and sets errno to ERANGE.

Example

CELEBL26

/* CELEBL26

   This exaxmple illustrates the lgammad64() function.

*/

#define __STDC_WANT_DEC_FP__
#include <math.h>
#include <stdio.h>
int main(void)
{
   _Decimal64 x, y;

   x = 42.0DD;
   y = lgammad64(x);

   printf ("lgammad64(%Df) = %Df\n", x, y);
}

lgammad32(), lgammad64(), lgammad128() - Log gamma function