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class Polynomial | |
def initialize(coefficients) | |
raise(ArgumentError, "Need at least 2 coefficients") if coefficients.size < 2 | |
@coefficients = coefficients | |
end | |
def to_s | |
return "0" if @coefficients.all? { |c| c == 0 } | |
polynomial = "" | |
@coefficients.each_with_index do |coefficient, index| | |
unless coefficient.zero? | |
operator = coefficient > 0 ? "+" : "-" | |
absolute = coefficient.abs | |
exponential = @coefficients.size - index - 1 | |
polynomial << operator if index > 0 or operator == "-" | |
polynomial << "#{absolute}" if (absolute > 1) or (exponential == 0 and absolute == 1) | |
polynomial << "x" if exponential >= 1 | |
polynomial << "^#{exponential}" if exponential > 1 | |
end | |
end | |
polynomial | |
end | |
end |
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require 'rubygems' | |
require 'spec' | |
require 'polynomial' | |
describe Polynomial do | |
context "creating a polynomial" do | |
it "should raise an error if arguments size < 2" do | |
lambda { Polynomial.new([1]) }.should raise_error("Need at least 2 coefficients") | |
end | |
it "should return 0 if all coefficients are 0" do | |
Polynomial.new([0, 0, 0]).to_s.should == "0" | |
end | |
it "should create a simple positive polynomial" do | |
Polynomial.new([2, 2]).to_s.should == "2x+2" | |
Polynomial.new([2, 2, 2]).to_s.should == "2x^2+2x+2" | |
Polynomial.new([4, 2, 2, 5]).to_s.should == "4x^3+2x^2+2x+5" | |
end | |
it "should ommit exponential 1 unless last" do | |
Polynomial.new([1, 2, 2]).to_s.should == "x^2+2x+2" | |
Polynomial.new([2, 1, 2]).to_s.should == "2x^2+x+2" | |
Polynomial.new([2, 2, 1]).to_s.should == "2x^2+2x+1" | |
end | |
it "should not print if coefficient is 0" do | |
Polynomial.new([2, 0, 2]).to_s.should == "2x^2+2" | |
Polynomial.new([2, 2, 0]).to_s.should == "2x^2+2x" | |
end | |
it "should print negative coefficients correctly" do | |
Polynomial.new([-5, 3, 1]).to_s.should == "-5x^2+3x+1" | |
Polynomial.new([ 5, -3, 1]).to_s.should == "5x^2-3x+1" | |
Polynomial.new([ 5, 3, -1]).to_s.should == "5x^2+3x-1" | |
Polynomial.new([-1, 3, -1]).to_s.should == "-x^2+3x-1" | |
end | |
end | |
end |
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