Method: MoreMath::Permutation#signum

Defined in:
lib/more_math/permutation.rb

#signum ⇒ Object Also known as: sgn

Returns the signum of this Permutation instance. It’s -1 if this permutation is odd and 1 if it’s an even permutation.

A permutation is odd if it can be represented by an odd number of transpositions (cycles of length 2), or even if it can be represented of an even number of transpositions.



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# File 'lib/more_math/permutation.rb', line 249

def signum
  s = 1
  cycles.each do |c|
    c.size % 2 == 0 and s *= -1
  end
  s
end