polynomial.rb

#!/usr/bin/ruby

class Polynomial

  def initialize(coefficients)
    if coefficients.length < 2
      raise ArgumentError, 'Need at least 2 coefficients.'
    end
    order = coefficients.length - 1
    @poly = ""
    coefficients.each do |c| 
      unless c == 0
        if order != coefficients.length - 1 and c > 0
          @poly << "+"
        end
        @poly << c.to_s unless c.abs == 1 
        @poly << "-" if c == -1
        @poly << "x" unless order < 1
        @poly << "^" + order.to_s unless order < 2
      end
      order -= 1
    end
  end

  def to_s
    @poly.empty? ? "0" : @poly
  end

end