lgamma, lgammaf, lgammal
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Determines the natural logarithm of the absolute value of the gamma function of the specified value.
Syntax
double lgamma(
double x
);
float lgamma(
float x
); //C++ only
long double lgamma(
long double x
); //C++ only
float lgammaf(
float x
);
long double lgammal(
long double x
);
Parameters
[in] 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, lgamma always takes and returns a double.
If x is a rational number, this function returns the logarithm of the factorial of (x-1).
Requirements
| Function | C header | C++ header |
|---|---|---|
lgamma, lgammaf, lgammal |
<math.h> | <cmath> |
For additional compatibility information, see Compatibility.