Compute the gamma function of a number
Synopsis:
#include <math.h> double tgamma( double x ); float tgammaf( float x ); long double tgammal( long double x );
Arguments:
- x
- An arbitrary number.
Description:
The tgamma(), tgammaf(), and tgammal() functions compute Γ(x), which is defined as follows:
To check for error situations, use feclearexcept() and fetestexcept(). For example:
- Call feclearexcept(FE_ALL_EXCEPT) before calling tgamma(), tgammaf(), or tgammal().
- On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.
Returns:
The gamma of x.
| If x is: | These functions return: | Errors: |
|---|---|---|
| A negative integer | NaN | FE_INVALID |
| ±0.0 | Inf, with the same sign as x | FE_DIVBYZERO |
| A value that would cause overflow | ±Inf, with the same sign as the correct value | FE_OVERFLOW |
| A value that would cause underflow | 0.0 | FE_UNDERFLOW |
| Subnormal and 1 / x is representable | 1 / x | — |
| NaN | NaN | — |
| Inf | Inf | FE_OVERFLOW |
| -Inf | NaN | FE_INVALID |
These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Interrupt handler | No |
| Signal handler | No |
| Thread | Yes |