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c99 [ flag... ] file... -lm [ library... ] #include <math.h> double tgamma(double x);
float tgammaf(float x);
long double tgammal(long double x);
These functions compute the gamma() function of x.
Upon successful completion, these functions return gamma(x).
If x is a negative integer, a domain error occurs and a NaN is returned.
If the correct value would cause overflow, a range error occurs and tgamma(), tgammaf(), and tgammal() return the value of the macro \(+-HUGE_VAL, \(+-HUGE_VALF, or \(+-HUGE_VALL, respectively.
If x is NaN, a NaN is returned.
If x is \(+-Inf, x is returned.
If x is \(+-0, a pole error occurs and tgamma(), tgammaf(), and tgammal() return \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL, respectively.
If x is +Inf, a domain error occurs and a NaN is returned.
These functions will fail if:
Domain Error
The value of x is a negative integer or x is -Inf. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception is raised.
Pole Error
The value of x is zero. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception is raised.
Range Error
The value overflows. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception is raised.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Interface Stability | Standard |
| MT-Level | MT-Safe |
feclearexcept(3M), fetestexcept(3M), lgamma(3M), math.h(3HEAD), attributes(5), standards(5)