normal?

# File lib/matrix.rb, line 709
  def normal?
    Matrix.Raise ErrDimensionMismatch unless square?
    rows.each_with_index do |row_i, i|
      rows.each_with_index do |row_j, j|
        s = 0
        rows.each_with_index do |row_k, k|
          s += row_i[k] * row_j[k].conj - row_k[i].conj * row_k[j]
        end
        return false unless s == 0
      end
    end
    true
  end