class MoreMath::Permutation

for example the result of a call to the Permutation#value method.
in the range of 0 and indices.size - 1. This is
indices, that should consist of a permutation of Fixnums
Creates a new Permutation instance from the Array

def self.from_value(indices)
  obj = new(indices.size)
  obj.instance_eval do
    self.rank = rank_indices(indices)
  end
  obj
end