Minor Description
The Zipf distribution is defined when the exponent is zero.
Zipf (Wikipedia)
Zipfian distribution (scipy)
Currently the RejectionInversionZipfSampler does not allow the exponent to be zero.
The PMF is:
pmf(x) = 1/x^s / Hn,s x in [1, n] n = number of elements s = exponent Hn,s is the Nth generalised harmonic number
In the case of a zero exponent the generalised harmonic number reduces to n and the PMF is:
pmf(x) = 1 / n
The distribution is a discrete uniform distribution.
I suggest extracting the sampling logic for the RejectionInversionZipfSampler into a nested class to be used as a delegate from the outer class's sample method. In the special case of a zero exponent the delegate can be replaced with a DiscreteUniformSampler.
