diemer · October 4, 2016 05:36
diff --git a/prime_sieve.rb b/prime_sieve.rb
 # An implementation of the Sieve of Eratosthenes in Ruby
 # I recently read about it in The Imposter's Handbook(https://bigmachine.io/products/the-imposters-handbook)
 # and thought it would be a fun experiment to try to code, just off the
 # description and the example animation on 
 # Wikipedia(https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes)

 class PrimeSieve
    def initialize(max)
       @numbers = (2...max).to_a
       @current_prime = 2
    end


    def primes
        while @current_prime <= @numbers.count
            mark_composite(@current_prime, @numbers)
            @current_prime += 1
        end
        @numbers
    end

    private
    def mark_composite(cp,n)
        mp = cp * 2
        n.count.times do
            n.delete(mp) if n.include? mp
            mp += cp
        end
    end
 end
diff --git a/prime_sieve_test.rb b/prime_sieve_test.rb
 require 'minitest/autorun'
 require './prime_sieve'

 class PrimeSieveTest < Minitest::Unit::TestCase

    def setup
        @sieve = PrimeSieve.new(200)
    end

    def test_first_number_is_two
        assert_equal 2, @sieve.primes.first
    end

    def test_prime_calculation
        expected_primes = "2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199"
        assert_equal @sieve.primes, expected_primes.split(", ").map {|i| i.to_i }
    end

 end
	# An implementation of the Sieve of Eratosthenes in Ruby
	# I recently read about it in The Imposter's Handbook(https://bigmachine.io/products/the-imposters-handbook)
	# and thought it would be a fun experiment to try to code, just off the
	# description and the example animation on
	# Wikipedia(https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes)

	class PrimeSieve
	def initialize(max)
	@numbers = (2...max).to_a
	@current_prime = 2
	end


	def primes
	while @current_prime <= @numbers.count
	mark_composite(@current_prime, @numbers)
	@current_prime += 1
	end
	@numbers
	end

	private
	def mark_composite(cp,n)
	mp = cp * 2
	n.count.times do
	n.delete(mp) if n.include? mp
	mp += cp
	end
	end
	end
	require 'minitest/autorun'
	require './prime_sieve'

	class PrimeSieveTest < Minitest::Unit::TestCase

	def setup
	@sieve = PrimeSieve.new(200)
	end

	def test_first_number_is_two
	assert_equal 2, @sieve.primes.first
	end

	def test_prime_calculation
	expected_primes = "2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199"
	assert_equal @sieve.primes, expected_primes.split(", ").map {\|i\| i.to_i }
	end

	end