README.md

• On your own, can you write a bit of code that prompts the user for a base-10 quantity then outputs it in binary, octal, and hex?

• Example:

  Quantity (base-10): 29
  
  base-2:  11101
  base-8:  35
  base-16: 1D
  

• Rules: Don’t use any built-in conversion available in your langugage of choice — that would be a little too easy, no? Try and figure out the mathematic approach. If you write tests it’s legit to use the built-in conversion in your test cases.

• Hint: You’re likely going to need the modulo operator, %, which outputs the remainder of division.

• Second hint: Build this iteratively — try to get just one conversion figured out before starting a second one.

converter.rb

class Converter
  def self.to_b(dec)
    modulus = dec % 2
    dividend = dec / 2
    
    if dividend == 0
      return modulus.to_s
    else
      return to_b(dividend) + modulus.to_s
    end    
  end

  def self.to_o(dec)
    modulus = dec % 8
    dividend = dec / 8
    
    if dividend == 0
      return modulus.to_s
    else
      return to_o(dividend) + modulus.to_s
    end    
  end

  def self.to_h(dec)
    modulus = dec % 16
    dividend = dec / 16
    
    if dividend == 0
      return hex_lookup(modulus)
    else
      return to_h(dividend) + hex_lookup(modulus)
    end    
  end

  def self.hex_lookup(decimal)
    [
      "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
      "A", "B", "C", "D", "E", "F"
    ][decimal]
  end
end

converter_test.rb

require 'minitest'
require 'minitest/autorun'
require './converter'

class ConverterTest < Minitest::Test

  def test_it_converts_single_digits_to_binary
    assert_equal "1", Converter.to_b(1)
    assert_equal "10", Converter.to_b(2)
    assert_equal "11", Converter.to_b(3)

    assert_equal "1000", Converter.to_b(8)
    assert_equal "1001", Converter.to_b(9)
  end

  def test_it_converts_single_digits_to_octal
    assert_equal "2", Converter.to_o(2)
    assert_equal "3", Converter.to_o(3)

    assert_equal "10", Converter.to_o(8)
    assert_equal "11", Converter.to_o(9)
  end

  def test_it_converts_to_hex
    assert_equal "2", Converter.to_h(2)
    assert_equal "F", Converter.to_h(15)

    assert_equal "10", Converter.to_h(16)
    assert_equal "11", Converter.to_h(17)

    assert_equal "FF", Converter.to_h(255)
  end
end

script.rb

require './converter'

print "Quantity (base-10): "
input = gets.chomp.to_i

output = "
base-2:  #{Converter.to_b(input)}
base-8:  #{Converter.to_o(input)}
base-16: #{Converter.to_h(input)}
"

puts output

Ummm... sorry. The input in the example was supposed to be 29!!!

(Since the binary ends in 1 the input must have been an odd number!)