TGAMMA(3M) Mathematical Library Functions TGAMMA(3M)

# NAME

tgamma, tgammaf, tgammal - compute gamma function

# SYNOPSIS

```c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double tgamma(double x);
```

```float tgammaf(float x);
```

```long double tgammal(long double x);
```

# DESCRIPTION

These functions compute the gamma() function of x.

# RETURN VALUES

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.

# ERRORS

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.

# USAGE

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.

# ATTRIBUTES

See attributes(7) for descriptions of the following attributes:

 ATTRIBUTE TYPE ATTRIBUTE VALUE Interface Stability Standard MT-Level MT-Safe