gistfile1.rb

#!/usr/bin/env ruby
# Polynomial beautifier, by Othmane Benkirane
require 'enumerator'
# Code
class Integer
  def sign
    self >= 0 ? '+' : '-'
  end
end
class Polynomial
  attr_accessor :output
  attr_reader :compression
  def initialize(numbers)
    numbers.shift while numbers.first == 0
    @numbers,@output = numbers,:ugly
    self.compression = :none
  end
  def compression=(compression)
    @b_,@a_ = case compression
    when :none; [' ', ' ']
    when :semi; [' ', '']
    when :full; ['','']
    else;       ['','']  
    end
  end
  def to_s
    numbers {|@num, @exp| [coef, exponent] unless coef.nil?}.
    reject {|l| l.nil?}.flatten.join
  end
  alias inspect to_s

  private
  def coef
    return nil if @num == 0
    "#{sign}#{out_number}"
  end

  def out_number
    @num.abs unless (@num == 1 || @num == -1) && @exp != 0
  end

  def sign
    if @exp == @numbers.size - 1
      "#{@num.sign}#@a_" if @num.sign == '-'
    else
      "#@b_#{@num.sign}#@a_"
    end
  end

  def exponent
    exp = @exp.to_s
    return 'x' if exp=='1'
    return ''  if exp=='0'
    output = case @output
      when :ugly; "^#{exp}"
      when :beautiful
        @@exponents ||= %w(⁰ ¹ ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹)
        exp.split('').map {|n| @@exponents[n.to_i]}.join
    end
    "x#{output}"
  end

  def numbers
    @numbers.reverse.enum_with_index.map do |num, exp|
      yield num, exp
    end.reverse
  end
end

# Test suite
if $0 == __FILE__
  require 'rubygems'
  require 'spec'
  describe "Polynomial" do
    before do
      @no_one   = Polynomial.new([1,1,1])
      @negative = Polynomial.new([-1,-2,-3])
      @zero     = Polynomial.new([0,1,2,3,0,4,0])
      @x1       = Polynomial.new([3,4])
      @long     = Polynomial.new((0..20).map{|l| l%5==0 ? 1 : 0}.reverse)
    end
    it 'should not show a coefficient equal to 1' do
      @no_one.to_s.should == 'x^2 + x + 1'
    end
    it 'should also support compacted output' do
      @no_one.compression = :full
      @no_one.to_s.should == 'x^2+x+1'
    end
    it 'should also support semi-compacted output' do
      @no_one.compression = :semi
      @no_one.to_s.should == 'x^2 +x +1'
    end
    it 'should not show + then -' do
      @negative.to_s.should == '- x^2 - 2x - 3'
    end
    it 'should not output zero polynomials' do
      @zero.to_s.should == 'x^5 + 2x^4 + 3x^3 + 4x'
    end
    it 'should not put ^1' do
      @x1.to_s.should == '3x + 4'
    end
    it 'should also output beautiful polynomials' do
      @long.output = :beautiful
      @long.to_s.should == 'x²⁰ + x¹⁵ + x¹⁰ + x⁵ + 1'
    end
  end
  Spec::Runner.run
end