RPCFN4_-_Pretty_Polynomial.rb

class Polynomial

  def initialize(coeffs)
    raise ArgumentError.new("Need at least 2 coefficients.") if coeffs.size < 2
    @coeffs = coeffs
  end

  def to_s
    output = []
    coeffs = @coeffs.dup
    coeffs.size.times do |index|
      coeff = coeffs.pop
      if coeff != 0
        output << "^#{index}" if index > 1
        output << 'x' if index > 0
        output << coeff
        output << '+' if coeff > 0 and
          coeffs.select { |c| c != 0 }.size > 0
      end
    end
    output.reverse.join
  end

end