std::tgamma

 

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Defined in header <cmath>
float       tgamma( float arg );		(since C++11)
double      tgamma( double arg );		(since C++11)
long double tgamma( long double arg );		(since C++11)
double      tgamma( Integral arg );		(since C++11)

Computes the gamma function of arg.

Parameters

arg

-

value of a floating-point or Integral type

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.

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.

Notes

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

Example

Run this code

#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

See also

lgamma (C++11)	natural logarithm of the gamma function (function)

External links

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