factorial(n) function

[Astralcircle]

Adds a simple E2 function to calculate the factorial of a number.

[Alexandre425]

Wouldn't it be more efficient to check whether n is greater than 171, returning +inf immediately?

[Astralcircle]

math.min protects against NaN

[CornerPin]

I think it would be better to precompute the results instead and store them in a lookup table for $O(1)$ time, otherwise the cost should be made proportional to n. Should probably return NaN for $n \lt 0$ as well.