Obfuscated factorial

[Joshua Landau]

On 26 October 2013 12:55, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> Just for fun:
...
> for i in range(16):
>     print(i, FactorialBuilder(i).build().calculate())

Python already supports the factorial operator, -ⵘ. You just have to import it.

# Import statement
ⵘ = type("",(),{"__rsub__":lambda s,n:(lambda f,n:f(f,n))(lambda
f,z:round((2.5066282746310002*(z+0j+7.5)**(z+0.5)*2.718281828459045**(-z-7.5)*(0.99999999999980993+676.5203681218851/(z+1)-1259.1392167224028/(z+2)+771.32342877765313/(z+3)-176.61502916214059/(z+4)+12.507343278686905/(z+5)-0.13857109526572012/(z+6)+9.9843695780195716e-6/(z+7)+1.5056327351493116e-7/(z+8))).real)if
z>=0.5 else 3.141592653589793/(__import__("math").sin(3.141592653589793*z)*f(f,1-z)),n)})()

assert 2-ⵘ == 2

assert 3-ⵘ == 6

assert 4-ⵘ == 24