A wrapper around an f64 to generate Exp(1) random numbers. Dividing by the desired rate lambda will give Exp(lambda) distributed random numbers.

A wrapper around an f64 to generate N(0, 1) random numbers (a.k.a. a standard normal, or Gaussian). Multiplying the generated values by the desired standard deviation sigma then adding the desired mean mu will give N(mu, sigma^2) distributed random numbers.