From 376becdbb3502672121bb1a62491db97ab335c20 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 05:47:12 +0000
Subject: [PATCH 01/19] 00_hello done

---
 00_hello/hello.rb | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 00_hello/hello.rb

diff --git a/00_hello/hello.rb b/00_hello/hello.rb
new file mode 100644
index 000000000..407219bd6
--- /dev/null
+++ b/00_hello/hello.rb
@@ -0,0 +1,7 @@
+def hello
+  "Hello!"
+end
+
+def greet(name="Stephen")
+  "Hello, #{name}!"
+end

From 647cd7cb4e851b13e7ec450769bfde6fa8ba3efb Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 05:51:33 +0000
Subject: [PATCH 02/19] 01_temperature done

---
 01_temperature/temperature.rb | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 01_temperature/temperature.rb

diff --git a/01_temperature/temperature.rb b/01_temperature/temperature.rb
new file mode 100644
index 000000000..77e0204f4
--- /dev/null
+++ b/01_temperature/temperature.rb
@@ -0,0 +1,7 @@
+def ftoc(f_temp)
+  ((f_temp - 32) * 5)/9
+end
+
+def ctof(c_temp)
+  ((c_temp * 9.0)/5.0)+32.0
+end

From a1c792d6aa20f9da15c142f54d288375d7195211 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 05:52:17 +0000
Subject: [PATCH 03/19] 01_temperature done

---
 01_temperature/temperature.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/01_temperature/temperature.rb b/01_temperature/temperature.rb
index 77e0204f4..1095a6223 100644
--- a/01_temperature/temperature.rb
+++ b/01_temperature/temperature.rb
@@ -1,5 +1,5 @@
 def ftoc(f_temp)
-  ((f_temp - 32) * 5)/9
+  ((f_temp - 32.0) * 5.0)/9.0
 end
 
 def ctof(c_temp)

From 5a57a8ecfd958533e7f6c0ec431f689e7e94110a Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 06:10:35 +0000
Subject: [PATCH 04/19] calculator done

---
 02_calculator/calculator.rb      | 38 ++++++++++++++++++++++++++++++++
 02_calculator/calculator_spec.rb | 38 ++++++++++++++++++++++++--------
 2 files changed, 67 insertions(+), 9 deletions(-)
 create mode 100644 02_calculator/calculator.rb

diff --git a/02_calculator/calculator.rb b/02_calculator/calculator.rb
new file mode 100644
index 000000000..f152af6ab
--- /dev/null
+++ b/02_calculator/calculator.rb
@@ -0,0 +1,38 @@
+def add(a, b)
+  a + b
+end
+
+def subtract(a, b)
+  a - b
+end
+
+def sum(nums_to_sum)
+  total = 0
+  nums_to_sum.each do |num|
+    total += num
+  end
+
+  return total
+end
+
+def multiply(nums_to_multiply=[])
+  total = 1
+  nums_to_multiply.each do |num|
+    total *= num
+  end
+
+  return total
+end
+
+def power(a, b)
+  a**b
+end
+
+def factorial(num)
+  total = 1
+  2.upto(num) do |product|
+    total *= product
+  end
+
+  return total
+end
diff --git a/02_calculator/calculator_spec.rb b/02_calculator/calculator_spec.rb
index fef7e9d00..f8ce2f497 100644
--- a/02_calculator/calculator_spec.rb
+++ b/02_calculator/calculator_spec.rb
@@ -79,21 +79,41 @@
 
 describe "#multiply" do
 
-  it "multiplies two numbers"
+  it "multiplies two numbers" do
+    expect(multiply([2,3])).to eq(6)
+  end
+
+  it "multiplies several numbers" do
+    expect(multiply([2,6,3,28])).to eq(1008)
+  end
 
-  it "multiplies several numbers"
-  
 end
 
 describe "#power" do
-  it "raises one number to the power of another number"
+  it "raises one number to the power of another number" do
+    expect(power(5,8)).to eq(390625)
+  end
 end
 
 # http://en.wikipedia.org/wiki/Factorial
 describe "#factorial" do
-  it "computes the factorial of 0"
-  it "computes the factorial of 1"
-  it "computes the factorial of 2"
-  it "computes the factorial of 5"
-  it "computes the factorial of 10"
+  it "computes the factorial of 0" do
+    expect(factorial(0)).to eq(1)
+  end
+
+  it "computes the factorial of 1" do
+    expect(factorial(1)).to eq(1)
+  end
+
+  it "computes the factorial of 2" do
+    expect(factorial(2)).to eq(2)
+  end
+
+  it "computes the factorial of 5" do
+    expect(factorial(5)).to eq(120)
+  end
+
+  it "computes the factorial of 10" do
+    expect(factorial(10)).to eq(3628800)
+  end
 end

From 0812987830edc87b30df1b2df01033b33806d27b Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 06:46:28 +0000
Subject: [PATCH 05/19] 03_simon_says_done

---
 03_simon_says/simon_says.rb | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 03_simon_says/simon_says.rb

diff --git a/03_simon_says/simon_says.rb b/03_simon_says/simon_says.rb
new file mode 100644
index 000000000..96d9c220f
--- /dev/null
+++ b/03_simon_says/simon_says.rb
@@ -0,0 +1,33 @@
+def echo(statement)
+  statement
+end
+
+def shout(statement)
+  statement.upcase
+end
+
+def repeat(input, n=2)
+  ([input] * n).join(' ')
+end
+
+def start_of_word(word, num)
+  word.slice(0..(num - 1))
+end
+
+def first_word(input)
+  input.split(' ')[0]
+end
+
+def titleize(input)
+  captilized = []
+  little_words = ['and', 'the', 'over']
+  input.split(' ').each_with_index do |word, ind|
+    if ind != 0 && little_words.include?(word)
+      captilized.push(word)
+    else
+      captilized.push(word.capitalize)
+    end
+  end
+
+  captilized.join(' ').to_s
+end

From 3968ad44a87fc18633bed7b58612fae0d5c9e474 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 27 Dec 2016 08:08:05 +0000
Subject: [PATCH 06/19] 04 pig_latin done

---
 04_pig_latin/pig_latin.rb      | 19 +++++++++++++++++++
 04_pig_latin/pig_latin_spec.rb |  5 +++++
 2 files changed, 24 insertions(+)
 create mode 100644 04_pig_latin/pig_latin.rb

diff --git a/04_pig_latin/pig_latin.rb b/04_pig_latin/pig_latin.rb
new file mode 100644
index 000000000..aed21b123
--- /dev/null
+++ b/04_pig_latin/pig_latin.rb
@@ -0,0 +1,19 @@
+def translate(input)
+  must_capitalize = true if input.capitalize == input
+  vowels = %w(a e i o u)
+  words_to_translate = input.split(' ')
+  translated_word = []
+  words_to_translate.each do |word|
+    if vowels.include?(word[0])
+      translated_word << word + 'ay'
+    else
+      ind = 0
+      ind += 1 until vowels.include?(word[ind]) && (word[ind-1] + word[ind] != 'qu')
+
+      translated_word << word.slice(ind...word.size) + word.slice(0...ind) + 'ay'
+    end
+  end
+
+  return translated_word.join(' ').capitalize if must_capitalize
+  return translated_word.join(' ')
+end
diff --git a/04_pig_latin/pig_latin_spec.rb b/04_pig_latin/pig_latin_spec.rb
index cc659edfd..4ea087a98 100644
--- a/04_pig_latin/pig_latin_spec.rb
+++ b/04_pig_latin/pig_latin_spec.rb
@@ -67,6 +67,11 @@
 
   # Test-driving bonus:
   # * write a test asserting that capitalized words are still capitalized (but with a different initial capital letter, of course)
+  it "must retain captilization after translation" do
+    s = translate("The quick brown fox")
+    expect(s).to eq("Ethay ickquay ownbray oxfay")
+  end
+
   # * retain the punctuation from the original phrase
 
 end

From 47947141d72b04a474f11ce47fba15c085fe72d6 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Wed, 28 Dec 2016 21:46:26 +0000
Subject: [PATCH 07/19] performance monitor done

---
 05_silly_blocks/silly_blocks.rb               | 13 +++++++++++++
 06_performance_monitor/performance_monitor.rb | 10 ++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 05_silly_blocks/silly_blocks.rb
 create mode 100644 06_performance_monitor/performance_monitor.rb

diff --git a/05_silly_blocks/silly_blocks.rb b/05_silly_blocks/silly_blocks.rb
new file mode 100644
index 000000000..dce329aae
--- /dev/null
+++ b/05_silly_blocks/silly_blocks.rb
@@ -0,0 +1,13 @@
+def reverser
+  yield.split.map { |word| word.reverse}.join(" ")
+end
+
+def adder(num=1)
+  yield + num
+end
+
+def repeater(loops=1)
+  loops.times do
+    yield
+  end
+end
diff --git a/06_performance_monitor/performance_monitor.rb b/06_performance_monitor/performance_monitor.rb
new file mode 100644
index 000000000..0275d953f
--- /dev/null
+++ b/06_performance_monitor/performance_monitor.rb
@@ -0,0 +1,10 @@
+def measure(num_times = 1)
+  avg_time = []
+  num_times.times do
+    beginning_time = Time.now
+    yield
+    avg_time << (Time.now - beginning_time)
+  end
+
+  return avg_time.inject{ |sum, el| sum + el }.to_f / avg_time.size
+end

From 8d0c74822d6dc68c3808c7d318ad0d2ec142e8bd Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Wed, 28 Dec 2016 21:48:11 +0000
Subject: [PATCH 08/19] performance_monitor complete

---
 06_performance_monitor/performance_monitor.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/06_performance_monitor/performance_monitor.rb b/06_performance_monitor/performance_monitor.rb
index 0275d953f..c3f545dc0 100644
--- a/06_performance_monitor/performance_monitor.rb
+++ b/06_performance_monitor/performance_monitor.rb
@@ -6,5 +6,5 @@ def measure(num_times = 1)
     avg_time << (Time.now - beginning_time)
   end
 
-  return avg_time.inject{ |sum, el| sum + el }.to_f / avg_time.size
+  return avg_time.inject{ |total_time, bench_time| total_time + bench_time }.to_f / avg_time.size
 end

From 6a839f003e4c6ee778ddae40bfe57c1ed989c7a0 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 03:38:46 +0000
Subject: [PATCH 09/19] 07 Hello Friend complete

---
 07_hello_friend/friend.rb | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 07_hello_friend/friend.rb

diff --git a/07_hello_friend/friend.rb b/07_hello_friend/friend.rb
new file mode 100644
index 000000000..858650aac
--- /dev/null
+++ b/07_hello_friend/friend.rb
@@ -0,0 +1,6 @@
+class Friend
+  def greeting(name=nil)
+    return "Hello, #{name}!" if name
+    "Hello!"
+  end
+end

From 69291b9d01885182d69cb4d5eb9dcbe7d0088d89 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 04:07:37 +0000
Subject: [PATCH 10/19] Done with 08_book_titles

---
 08_book_titles/book.rb | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 08_book_titles/book.rb

diff --git a/08_book_titles/book.rb b/08_book_titles/book.rb
new file mode 100644
index 000000000..790b84f35
--- /dev/null
+++ b/08_book_titles/book.rb
@@ -0,0 +1,25 @@
+class Book
+  def initialize(title = nil)
+    @title = title
+    @exclusion_words = %w(the a an and in of)
+  end
+
+  def title
+    capitalize_each(@title)
+  end
+
+  def title=(title)
+    capitalize_each(@title = title)
+  end
+
+  def capitalize_each(title)
+    capitalized_title = title.split.each_with_index.map do |v, i|
+      if i == 0 || !@exclusion_words.include?(v)
+        v.capitalize
+      else
+        v
+      end
+    end
+    capitalized_title.join(' ')
+  end
+end

From 3b6909a2e87bec8ad16806ab4e2931f41959d5ff Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 04:21:21 +0000
Subject: [PATCH 11/19] 09 timer done

---
 09_timer/timer.rb | 11 +++++++++++
 1 file changed, 11 insertions(+)
 create mode 100644 09_timer/timer.rb

diff --git a/09_timer/timer.rb b/09_timer/timer.rb
new file mode 100644
index 000000000..2fc6bf910
--- /dev/null
+++ b/09_timer/timer.rb
@@ -0,0 +1,11 @@
+class Timer
+  attr_accessor :seconds
+
+  def initialize
+    self.seconds = 0
+  end
+
+  def time_string
+    Time.at(self.seconds).utc.strftime("%H:%M:%S")
+  end
+end

From 53c8e8f48445c6874f5af90694e4820f3eb79b09 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 05:22:53 +0000
Subject: [PATCH 12/19] 10 temperature object done

---
 10_temperature_object/temperature.rb | 63 ++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 10_temperature_object/temperature.rb

diff --git a/10_temperature_object/temperature.rb b/10_temperature_object/temperature.rb
new file mode 100644
index 000000000..3b391929f
--- /dev/null
+++ b/10_temperature_object/temperature.rb
@@ -0,0 +1,63 @@
+class Temperature
+  attr_accessor :temp
+
+  def initialize(options={})
+    @temp = options
+  end
+
+  def in_fahrenheit
+    if temp[:f]
+      return temp[:f]
+    else
+      return ((temp[:c] * 9.0)/5.0)+32.0
+    end
+  end
+
+  def in_celsius
+    if temp[:c]
+      return temp[:c]
+    else
+      return ((temp[:f] - 32.0) * 5.0)/9.0
+    end
+  end
+
+  def self.from_celsius(temp)
+    return Temperature.new(:c => temp)
+  end
+
+  def self.from_fahrenheit(temp)
+    return Temperature.new(:f => temp)
+  end
+end
+
+class Celsius < Temperature
+  attr_accessor :temp
+
+  def initilize(temp)
+    @temp = temp
+  end
+
+  def in_celsius
+    return temp
+  end
+
+  def in_fahrenheit
+    return ((temp * 9.0)/5.0)+32.0
+  end
+end
+
+class Fahrenheit < Temperature
+  attr_accessor :temp
+
+  def initilize(temp)
+    @temp = temp
+  end
+
+  def in_celsius
+    return ((temp  - 32.0) * 5.0)/9.0
+  end
+
+  def in_fahrenheit
+    return temp
+  end
+end

From c76c184787a29dc8aa5a5e07a2b4de7660dd3c02 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 06:03:34 +0000
Subject: [PATCH 13/19] 11 dictionary done

---
 11_dictionary/dictionary.rb | 38 +++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 11_dictionary/dictionary.rb

diff --git a/11_dictionary/dictionary.rb b/11_dictionary/dictionary.rb
new file mode 100644
index 000000000..d89b15e65
--- /dev/null
+++ b/11_dictionary/dictionary.rb
@@ -0,0 +1,38 @@
+class Dictionary
+  attr_accessor :entries
+
+  def initialize (entries = {})
+    @entries = entries
+  end
+
+  def add(words={})
+    if words.is_a? String
+      entries[words] = nil
+    else
+      words.each_pair do |word, definition|
+        entries[word] = definition
+      end
+    end
+  end
+
+  def keywords
+    entries.keys.sort
+  end
+
+  def include?(word)
+    entries.has_key?(word)
+  end
+
+  def find(word)
+    return entries.select{|k,v| k.start_with? word} || {}
+  end
+
+  def printable
+    printable_list = ""
+    entries.sort.each do |value|
+      printable_list << "[#{value[0]}] \"#{value[1]}\"\n"
+    end
+
+    printable_list.strip
+  end
+end

From 786d676acb38e4241cda8812f1dd1eddeee88cc9 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 06:54:46 +0000
Subject: [PATCH 14/19] 12 rpn calculator done

---
 12_rpn_calculator/rpn_calculator.rb | 87 +++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 12_rpn_calculator/rpn_calculator.rb

diff --git a/12_rpn_calculator/rpn_calculator.rb b/12_rpn_calculator/rpn_calculator.rb
new file mode 100644
index 000000000..aaa4a7bce
--- /dev/null
+++ b/12_rpn_calculator/rpn_calculator.rb
@@ -0,0 +1,87 @@
+class RPNCalculator
+  attr_accessor :stack
+
+  def initialize
+    @stack = []
+  end
+
+  def push(num)
+    @stack.push(num)
+  end
+
+  def plus
+    empty_array?
+    b, a = populate_numbers
+    result = a + b
+    @stack.push(result)
+
+    nil
+  end
+
+  def minus
+    empty_array?
+    b, a = populate_numbers
+    result = a - b
+    @stack.push(result)
+
+    nil
+  end
+
+  def times
+    empty_array?
+    b, a = populate_numbers
+    result = a * b
+    @stack.push(result)
+
+    nil
+  end
+
+  def divide
+    empty_array?
+    b, a = populate_numbers
+    result = a.to_f / b.to_f
+    @stack.push(result)
+
+    nil
+  end
+
+  def empty_array?
+    raise 'calculator is empty' if @stack == []
+  end
+
+  def populate_numbers
+    b = stack.pop
+    a = stack.pop
+    [b, a]
+  end
+
+  def tokens(str)
+    str.split.map! { |t| t[/\d/] ? t.to_i : t.to_sym }
+  end
+
+  def evaluate(str)
+    temp_array = str.split
+    temp_array.each do |t|
+      if t[/\d/]
+        @stack.push(t.to_i)
+      else
+        case t
+        when '*'
+          self.times
+        when '/'
+          self.divide
+        when '+'
+          self.plus
+        when '-'
+          self.minus
+        end
+      end
+    end
+    
+    value
+  end
+
+  def value
+    @stack[-1]
+  end
+end

From 8a77bd7ad6e8fa6e7221f9d3df8fbbd6d3e68d03 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 07:44:55 +0000
Subject: [PATCH 15/19] 13 xml_document done

---
 13_xml_document/xml_document.rb | 84 +++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 13_xml_document/xml_document.rb

diff --git a/13_xml_document/xml_document.rb b/13_xml_document/xml_document.rb
new file mode 100644
index 000000000..172b19149
--- /dev/null
+++ b/13_xml_document/xml_document.rb
@@ -0,0 +1,84 @@
+class XmlDocument
+  attr_accessor :indent, :indent_count
+
+  def initialize(indent = false)
+    @indent = indent
+    @indent_count = 0
+  end
+
+  def hello(options = {})
+    builder = ''
+    builder = " name='#{options[:name]}'" if options[:name]
+
+    if block_given?
+      built_xml = ''
+      if @indent
+        indent_space = increase_indent
+        built_xml = "#{indent_space}<hello>\n#{yield}#{indent_space}</hello>\n"
+      else
+        built_xml = "<hello>#{yield}</hello>"
+      end
+
+      return built_xml
+    end
+
+    "<hello#{builder}/>"
+  end
+
+  def goodbye
+    builder = ''
+    if block_given?
+      built_xml = ''
+      if @indent
+        indent_space = increase_indent
+        built_xml = "#{indent_space}<goodbye>\n#{yield}#{indent_space}</goodbye>\n"
+      else
+        built_xml = "<goodbye>#{yield}</goodbye>"
+      end
+
+      return built_xml
+    end
+
+    "<goodbye#{builder}/>"
+  end
+
+  def come_back
+    builder = ''
+    if block_given?
+      built_xml = ''
+      if @indent
+        indent_space = increase_indent
+        built_xml = "#{indent_space}<come_back>\n#{yield}#{indent_space}</come_back>\n"
+      else
+        built_xml = "<come_back>#{yield}</come_back>"
+      end
+
+      return built_xml
+    end
+
+    "<come_back#{builder}/>"
+  end
+
+  def ok_fine(options = {})
+    builder = ''
+    builder = " be='#{options[:be]}'" if options[:be]
+    return "<ok_fine>#{yield}</ok_fine>" if block_given?
+
+    if @indent
+      indent_space = increase_indent
+      return "#{indent_space}<ok_fine#{builder}/>\n"
+    else
+      return "<ok_fine#{builder}/>"
+    end
+  end
+
+  def increase_indent
+    indent_space = '  ' * @indent_count
+    @indent_count = 1 + @indent_count
+    return indent_space
+  end
+
+  def send(tag_name)
+    "<#{tag_name}/>"
+  end
+end

From 7c79c472ed9e82c9690405cd6f112e7b75c1608c Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 07:53:07 +0000
Subject: [PATCH 16/19] code changes

---
 13_xml_document/xml_document.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/13_xml_document/xml_document.rb b/13_xml_document/xml_document.rb
index 172b19149..cb59d0207 100644
--- a/13_xml_document/xml_document.rb
+++ b/13_xml_document/xml_document.rb
@@ -6,7 +6,7 @@ def initialize(indent = false)
     @indent_count = 0
   end
 
-  def hello(options = {})
+  def hello(options = {}, &block)
     builder = ''
     builder = " name='#{options[:name]}'" if options[:name]
 

From 090845fbf2c6dc3bc04561948d2961d91064ff31 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 08:03:02 +0000
Subject: [PATCH 17/19] cleaned up xml_doc code

---
 13_xml_document/xml_document.rb | 66 +++++++++++----------------------
 1 file changed, 22 insertions(+), 44 deletions(-)

diff --git a/13_xml_document/xml_document.rb b/13_xml_document/xml_document.rb
index cb59d0207..7891da45e 100644
--- a/13_xml_document/xml_document.rb
+++ b/13_xml_document/xml_document.rb
@@ -7,62 +7,28 @@ def initialize(indent = false)
   end
 
   def hello(options = {}, &block)
-    builder = ''
     builder = " name='#{options[:name]}'" if options[:name]
 
-    if block_given?
-      built_xml = ''
-      if @indent
-        indent_space = increase_indent
-        built_xml = "#{indent_space}<hello>\n#{yield}#{indent_space}</hello>\n"
-      else
-        built_xml = "<hello>#{yield}</hello>"
-      end
-
-      return built_xml
-    end
+    return xml_builder('hello', &block) if block_given?
 
     "<hello#{builder}/>"
   end
 
-  def goodbye
-    builder = ''
-    if block_given?
-      built_xml = ''
-      if @indent
-        indent_space = increase_indent
-        built_xml = "#{indent_space}<goodbye>\n#{yield}#{indent_space}</goodbye>\n"
-      else
-        built_xml = "<goodbye>#{yield}</goodbye>"
-      end
-
-      return built_xml
-    end
+  def goodbye(_options = {}, &block)
+    return xml_builder('goodbye', &block) if block_given?
 
-    "<goodbye#{builder}/>"
+    "<goodbye/>"
   end
 
-  def come_back
-    builder = ''
-    if block_given?
-      built_xml = ''
-      if @indent
-        indent_space = increase_indent
-        built_xml = "#{indent_space}<come_back>\n#{yield}#{indent_space}</come_back>\n"
-      else
-        built_xml = "<come_back>#{yield}</come_back>"
-      end
+  def come_back(_options = {}, &block)
+    return xml_builder('come_back', &block) if block_given?
 
-      return built_xml
-    end
-
-    "<come_back#{builder}/>"
+    "<come_back/>"
   end
 
-  def ok_fine(options = {})
-    builder = ''
+  def ok_fine(options = {}, &block)
     builder = " be='#{options[:be]}'" if options[:be]
-    return "<ok_fine>#{yield}</ok_fine>" if block_given?
+    return xml_builder('ok_fine', &block) if block_given?
 
     if @indent
       indent_space = increase_indent
@@ -72,10 +38,22 @@ def ok_fine(options = {})
     end
   end
 
+  def xml_builder(caller)
+    built_xml = ''
+    if @indent
+      indent_space = increase_indent
+      built_xml = "#{indent_space}<#{caller}>\n#{yield}#{indent_space}</#{caller}>\n"
+    else
+      built_xml = "<#{caller}>#{yield}</#{caller}>"
+    end
+
+    built_xml
+  end
+
   def increase_indent
     indent_space = '  ' * @indent_count
     @indent_count = 1 + @indent_count
-    return indent_space
+    indent_space
   end
 
   def send(tag_name)

From 5efe67db861aaad9bf76bacda7615ea56495aeb5 Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 08:19:45 +0000
Subject: [PATCH 18/19] 14 array_extenstions done

---
 13_xml_document/xml_document.rb         |  4 ++--
 14_array_extensions/array_extensions.rb | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)
 create mode 100644 14_array_extensions/array_extensions.rb

diff --git a/13_xml_document/xml_document.rb b/13_xml_document/xml_document.rb
index 7891da45e..9440b629b 100644
--- a/13_xml_document/xml_document.rb
+++ b/13_xml_document/xml_document.rb
@@ -17,13 +17,13 @@ def hello(options = {}, &block)
   def goodbye(_options = {}, &block)
     return xml_builder('goodbye', &block) if block_given?
 
-    "<goodbye/>"
+    '<goodbye/>'
   end
 
   def come_back(_options = {}, &block)
     return xml_builder('come_back', &block) if block_given?
 
-    "<come_back/>"
+    '<come_back/>'
   end
 
   def ok_fine(options = {}, &block)
diff --git a/14_array_extensions/array_extensions.rb b/14_array_extensions/array_extensions.rb
new file mode 100644
index 000000000..d66363439
--- /dev/null
+++ b/14_array_extensions/array_extensions.rb
@@ -0,0 +1,13 @@
+class Array
+  def sum
+    inject(0) { |sum, n| sum + n }
+  end
+
+  def square
+    map { |x| x**2 }
+  end
+
+  def square!
+    map! { |x| x**2 }
+  end
+end

From a8508e1e6ce880c737279d2c7c655fa7dfc42a1b Mon Sep 17 00:00:00 2001
From: Stephen Akuffo <slyven@gmail.com>
Date: Tue, 3 Jan 2017 08:36:19 +0000
Subject: [PATCH 19/19] done

---
 15_in_words/in_words.rb | 61 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 15_in_words/in_words.rb

diff --git a/15_in_words/in_words.rb b/15_in_words/in_words.rb
new file mode 100644
index 000000000..db2c8be2c
--- /dev/null
+++ b/15_in_words/in_words.rb
@@ -0,0 +1,61 @@
+class Integer
+  ONES = %w(#{nil} one two three four five six seven eight nine).freeze
+  TEENS = %w(ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen).freeze
+  TENS = %w(ten twenty thirty forty fifty sixty seventy eighty ninety).freeze
+
+  def translate(number, str = '', last = false)
+    return str if number == 0
+    if number / 100 > 0
+      remainder = number % 100
+      number /= 100
+      str += ' ' + ONES[number] + ' hundred'
+    elsif number.between?(10, 19)
+      str += if last
+               ' ' + TEENS[number - 10]
+             else
+               ' ' + TEENS[number - 10]
+             end
+      return str
+    elsif number / 10 > 0
+      remainder = number % 10
+      number /= 10
+      str += if last
+               ' ' + TENS[number - 1]
+             else
+               ' ' + TENS[number - 1]
+             end
+    else
+      str += ' ' + ONES[number]
+      remainder = 0
+    end
+    translate(remainder, str, true)
+  end
+
+  def in_words(str = '')
+    now_writing = self
+    return 'zero' if now_writing == 0
+    case
+    when now_writing / 1_000_000_000_000 > 0
+      to_write = now_writing % 1_000_000_000_000
+      now_writing /= 1_000_000_000_000
+      str += translate(now_writing) + ' trillion'
+    when now_writing / 1_000_000_000 > 0
+      to_write = now_writing % 1_000_000_000
+      now_writing /= 1_000_000_000
+      str += translate(now_writing) + ' billion'
+    when now_writing / 1_000_000 > 0
+      to_write = now_writing % 1_000_000
+      now_writing /= 1_000_000
+      str += translate(now_writing) + ' million'
+    when now_writing / 1000 > 0
+      to_write = now_writing % 1000
+      now_writing /= 1000
+      str += translate(now_writing) + ' thousand'
+    else
+      str += translate(now_writing)
+      return str[1..-1]
+    end
+    return str[1..-1] if to_write == 0
+    to_write.in_words(str)
+  end
+end