Factorial Algorithms in different languages

Answer 1

D Templates: Functional

template factorial(int n : 1)
{
  const factorial = 1;
}

template factorial(int n)
{
  const factorial =
     n * factorial!(n-1);
}

or

template factorial(int n)
{
  static if(n == 1)
    const factorial = 1;
  else 
    const factorial =
       n * factorial!(n-1);
}

Used like this:

factorial!(5)