class MoreMath::Permutation

def power(n)

Negative powers are taken to be powers of the inverse.
Computes the nth power (ie the nth repeated permutation) of this instance. 
def power(n)
  if n.respond_to?(:to_int)
    n = n.to_int
  else
    raise TypeError, "#{n.inspect} cannot be converted to an integer"
  end
  if n >= 0
    (1..n).inject(identity) { |p, e| p * self }
  else # negative powers are taken to be powers of the inverse
    -power(-n)
  end
end