Crate factorial

Compute the factorial

This crate provides some convenient and safe methods to compute the factorial and related functions the most naive way possible.

They are not necessarily the fastest versions: there are prime sieve methods that compute the factorial in O(n (log n loglog n)^2). Patches are welcome.

Traits

DoubleFactorial	Unary operator for computing the double factorial of a number
Factorial	Unary operator for computing the factorial of a number