std::tgamma

From Cppreference

Computes the gamma function of arg.

[edit] Parameters

[edit] Return value

The value of the gamma function of arg, that is ∫∞
0targ-1
e^-t dt.

If arg is a natural number, std::tgamma(arg) is the factorial of arg-1.

[edit] Exceptions

If arg is negative, domain error may occur and FE_INVALID may be raised.

If arg is zero, pole error may occur and FE_DIVBYZERO may be raised.

If arg is too large, range error may occur and FE_OVERFLOW may be raised.

If arg is too small, range error may occur and FE_UNDERFLOW may be raised.

[edit] Notes

Many implementations calculate the exact integer-domain factorial if the argument is a sufficiently small integer.

[edit] Example

#include <iostream>
#include <cmath>
double factorial(double arg)
{
    return std::tgamma(arg + 1);
}
int main()
{
    std::cout << "The factorial of 5 is " << factorial(5) << '\n'
              << "The factorial of 100 is " << factorial(100) << '\n';
}

Output:

The factorial of 5 is 120
The factorial of 100 is 9.33262e+157

[edit] See also

[edit] External links

Weisstein, Eric W. "Gamma Function." From MathWorld--A Wolfram Web Resource.