Recap - Fractions

Part of the Object Oriented Programming section of Coddy's Ruby journey. Lesson 41 of 57.

Challenge

Hard

Complete the value class Frac. initialize(num, den) reduces the fraction and keeps the sign on the numerator, raising ZeroDivisionError with zero denominator when den is 0. Define +, -, * and / returning new fractions (/ by a zero fraction raises ZeroDivisionError with division by zero), -@, ==, eql? and hash so equal fractions are the same Hash key, and <=> with Comparable. to_s returns 3/4, or 2 when the denominator is 1.

The supplied code reads commands: 1/2 + 1/3 (any of the four operators), neg 3/4, sort 1/2 1/3 3/4, max 1/2 2/3, uniq 1/2 2/4 1/3 (printing the count and the distinct fractions) and cmp 1/2 2/4 (printing =, < or >). Errors print their message.

Your code goes in frac.rb. main.rb holds the supplied input/output code and cannot be edited.

Try it yourself

require_relative 'frac'

# Supplied input/output code: keep it as it is
input = []
while (line = gets)
  input << line.chomp
end
def frac(text)
  n, d = text.split("/").map(&:to_i)
  Frac.new(n, d || 1)
end

input.each do |line|
  parts = line.split
  begin
    case parts[0]
    when "neg" then puts(-frac(parts[1]))
    when "sort" then puts parts[1..].map { |t| frac(t) }.sort.join(" ")
    when "max" then puts parts[1..].map { |t| frac(t) }.max
    when "uniq"
      distinct = parts[1..].map { |t| frac(t) }.uniq
      puts "#{distinct.size}: #{distinct.join(" ")}"
    when "cmp"
      order = frac(parts[1]) <=> frac(parts[2])
      puts ["<", "=", ">"][order + 1]
    else
      a = frac(parts[0])
      b = frac(parts[2])
      puts a.public_send(parts[1], b)
    end
  rescue ZeroDivisionError => e
    puts e.message
  end
end