diff --git a/tests/results/1 b/tests/results/1
index b83ed07..8b7a51e 100644
--- a/tests/results/1
+++ b/tests/results/1
@@ -1,10 +1,12 @@
+1_Inheritance
 1line
+2_Multiple_Inheritance
 :learn
 :list
 Advanced
 Classes
 Comments
-Control_Flow
+Control_Flow_and_Iterables
 Functions
 Modules
 Primitive_Datatypes_and_Operators
@@ -13,6 +15,7 @@ doc
 func
 hello
 lambda
+list_comprehension
 loops
 recursion
 rosetta/
diff --git a/tests/results/15 b/tests/results/15
index bc1df86..237ec80 100644
--- a/tests/results/15
+++ b/tests/results/15
@@ -1,361 +1,384 @@
-# Single line comments start with a number symbol.
+# Single line comments start with a number symbol.
 
 """ Multiline strings can be written
     using three "s, and are often used
-    as comments
+    as documentation.
 """
 
-####################################################
-# 1. Primitive Datatypes and Operators
-####################################################
+####################################################
+## 1. Primitive Datatypes and Operators
+####################################################
 
-# You have numbers
-3  # => 3
+# You have numbers
+3  # => 3
 
-# Math is what you would expect
-1 + 1  # => 2
-8 - 1  # => 7
-10 * 2  # => 20
-35 / 5  # => 7
+# Math is what you would expect
+1 + 1   # => 2
+8 - 1   # => 7
+10 * 2  # => 20
+35 / 5  # => 7.0
 
-# Division is a bit tricky. It is integer division and floors the results
-# automatically.
-5 / 2  # => 2
+# Integer division rounds down for both positive and negative numbers.
+5 // 3       # => 1
+-5 // 3      # => -2
+5.0 // 3.0   # => 1.0 # works on floats too
+-5.0 // 3.0  # => -2.0
 
-# To fix division we need to learn about floats.
-2.0  # This is a float
-11.0 / 4.0  # => 2.75 ahhh...much better
+# The result of division is always a float
+10.0 / 3  # => 3.3333333333333335
 
-# Result of integer division truncated down both for positive and negative.
-5 // 3  # => 1
-5.0 // 3.0  # => 1.0 # works on floats too
--5 // 3  # => -2
--5.0 // 3.0  # => -2.0
+# Modulo operation
+7 % 3  # => 1
 
-# Note that we can also import division module(Section 6 Modules)
-# to carry out normal division with just one '/'.
-from __future__ import division
+# Exponentiation (x**y, x to the yth power)
+2**3  # => 8
 
-11 / 4  # => 2.75  ...normal division
-11 // 4  # => 2 ...floored division
+# Enforce precedence with parentheses
+1 + 3 * 2  # => 7
+(1 + 3) * 2  # => 8
 
-# Modulo operation
-7 % 3  # => 1
+# Boolean values are primitives (Note: the capitalization)
+True  # => True
+False  # => False
 
-# Exponentiation (x to the yth power)
-2 ** 4  # => 16
+# negate with not
+not True   # => False
+not False  # => True
 
-# Enforce precedence with parentheses
-(1 + 3) * 2  # => 8
+# Boolean Operators
+# Note "and" and "or" are case-sensitive
+True and False  # => False
+False or True   # => True
 
-# Boolean Operators
-# Note "and" and "or" are case-sensitive
-True and False  # => False
-False or True  # => True
+# True and False are actually 1 and 0 but with different keywords
+True + True # => 2
+True * 8    # => 8
+False - 5   # => -5
 
-# Note using Bool operators with ints
-0 and 2  # => 0
--5 or 0  # => -5
-0 == False  # => True
-2 == True  # => False
-1 == True  # => True
+# Comparison operators look at the numerical value of True and False
+0 == False  # => True
+1 == True   # => True
+2 == True   # => False
+-5 != False # => True
 
-# negate with not
-not True  # => False
-not False  # => True
+# Using boolean logical operators on ints casts them to booleans for evaluation, but their non-cast value is returned
+# Don't mix up with bool(ints) and bitwise and/or (&,|)
+bool(0)     # => False
+bool(4)     # => True
+bool(-6)    # => True
+0 and 2     # => 0
+-5 or 0     # => -5
 
-# Equality is ==
-1 == 1  # => True
-2 == 1  # => False
+# Equality is ==
+1 == 1  # => True
+2 == 1  # => False
 
-# Inequality is !=
-1 != 1  # => False
-2 != 1  # => True
+# Inequality is !=
+1 != 1  # => False
+2 != 1  # => True
 
-# More comparisons
-1 < 10  # => True
-1 > 10  # => False
-2 <= 2  # => True
-2 >= 2  # => True
+# More comparisons
+1 < 10  # => True
+1 > 10  # => False
+2 <= 2  # => True
+2 >= 2  # => True
 
-# Comparisons can be chained!
-1 < 2 < 3  # => True
-2 < 3 < 2  # => False
+# Seeing whether a value is in a range
+1 < 2 and 2 < 3  # => True
+2 < 3 and 3 < 2  # => False
+# Chaining makes this look nicer
+1 < 2 < 3  # => True
+2 < 3 < 2  # => False
 
-# Strings are created with " or '
+# (is vs. ==) is checks if two variables refer to the same object, but == checks
+# if the objects pointed to have the same values.
+a = [1, 2, 3, 4]  # Point a at a new list, [1, 2, 3, 4]
+b = a             # Point b at what a is pointing to
+b is a            # => True, a and b refer to the same object
+b == a            # => True, a's and b's objects are equal
+b = [1, 2, 3, 4]  # Point b at a new list, [1, 2, 3, 4]
+b is a            # => False, a and b do not refer to the same object
+b == a            # => True, a's and b's objects are equal
+
+# Strings are created with " or '
 "This is a string."
 'This is also a string.'
 
-# Strings can be added too!
-"Hello " + "world!"  # => "Hello world!"
-# Strings can be added without using '+'
-"Hello " "world!"  # => "Hello world!"
+# Strings can be added too! But try not to do this.
+"Hello " + "world!"  # => "Hello world!"
+# String literals (but not variables) can be concatenated without using '+'
+"Hello " "world!"    # => "Hello world!"
 
-# ... or multiplied
-"Hello" * 3  # => "HelloHelloHello"
+# A string can be treated like a list of characters
+"Hello world!"[0]  # => 'H'
 
-# A string can be treated like a list of characters
-"This is a string"[0]  # => 'T'
+# You can find the length of a string
+len("This is a string")  # => 16
 
-# You can find the length of a string
-len("This is a string")  # => 16
-
-# String formatting with %
-# Even though the % string operator will be deprecated on Python 3.1 and removed
-# later at some time, it may still be good to know how it works.
-x = 'apple'
-y = 'lemon'
-z = "The items in the basket are %s and %s" % (x, y)
-
-# A newer way to format strings is the format method.
-# This method is the preferred way
-"{} is a {}".format("This", "placeholder")
-"{0} can be {1}".format("strings", "formatted")
-# You can use keywords if you don't want to count.
-"{name} wants to eat {food}".format(name="Bob", food="lasagna")
-
-# None is an object
-None  # => None
-
-# Don't use the equality "==" symbol to compare objects to None
-# Use "is" instead
-"etc" is None  # => False
-None is None  # => True
-
-# The 'is' operator tests for object identity. This isn't
-# very useful when dealing with primitive values, but is
-# very useful when dealing with objects.
-
-# Any object can be used in a Boolean context.
-# The following values are considered falsey:
-#    - None
-#    - zero of any numeric type (e.g., 0, 0L, 0.0, 0j)
-#    - empty sequences (e.g., '', (), [])
-#    - empty containers (e.g., {}, set())
-#    - instances of user-defined classes meeting certain conditions
-#      see: https://docs.python.org/2/reference/datamodel.html#object.__nonzero__
-#
-# All other values are truthy (using the bool() function on them returns True).
-bool(0)  # => False
-bool("")  # => False
+# You can also format using f-strings or formatted string literals (in Python 3.6+)
+name = "Reiko"
+f"She said her name is {name}." # => "She said her name is Reiko"
+# You can basically put any Python statement inside the braces and it will be output in the string.
+f"{name} is {len(name)} characters long." # => "Reiko is 5 characters long."
 
 
-####################################################
-# 2. Variables and Collections
-####################################################
+# None is an object
+None  # => None
 
-# Python has a print statement
-print "I'm Python. Nice to meet you!"  # => I'm Python. Nice to meet you!
+# Don't use the equality "==" symbol to compare objects to None
+# Use "is" instead. This checks for equality of object identity.
+"etc" is None  # => False
+None is None   # => True
 
-# Simple way to get input data from console
-input_string_var = raw_input(
-    "Enter some data: ")  # Returns the data as a string
-input_var = input("Enter some data: ")  # Evaluates the data as python code
-# Warning: Caution is recommended for input() method usage
-# Note: In python 3, input() is deprecated and raw_input() is renamed to input()
+# None, 0, and empty strings/lists/dicts/tuples all evaluate to False.
+# All other values are True
+bool(0)   # => False
+bool("")  # => False
+bool([])  # => False
+bool({})  # => False
+bool(())  # => False
 
-# No need to declare variables before assigning to them.
-some_var = 5  # Convention is to use lower_case_with_underscores
-some_var  # => 5
+####################################################
+## 2. Variables and Collections
+####################################################
 
-# Accessing a previously unassigned variable is an exception.
-# See Control Flow to learn more about exception handling.
-some_other_var  # Raises a name error
+# Python has a print function
+print("I'm Python. Nice to meet you!")  # => I'm Python. Nice to meet you!
 
-# if can be used as an expression
-# Equivalent of C's '?:' ternary operator
-"yahoo!" if 3 > 2 else 2  # => "yahoo!"
+# By default the print function also prints out a newline at the end.
+# Use the optional argument end to change the end string.
+print("Hello, World", end="!")  # => Hello, World!
 
-# Lists store sequences
+# Simple way to get input data from console
+input_string_var = input("Enter some data: ") # Returns the data as a string
+# Note: In earlier versions of Python, input() method was named as raw_input()
+
+# There are no declarations, only assignments.
+# Convention is to use lower_case_with_underscores
+some_var = 5
+some_var  # => 5
+
+# Accessing a previously unassigned variable is an exception.
+# See Control Flow to learn more about exception handling.
+some_unknown_var  # Raises a NameError
+
+# if can be used as an expression
+# Equivalent of C's '?:' ternary operator
+"yahoo!" if 3 > 2 else 2  # => "yahoo!"
+
+# Lists store sequences
 li = []
-# You can start with a prefilled list
+# You can start with a prefilled list
 other_li = [4, 5, 6]
 
-# Add stuff to the end of a list with append
-li.append(1)  # li is now [1]
-li.append(2)  # li is now [1, 2]
-li.append(4)  # li is now [1, 2, 4]
-li.append(3)  # li is now [1, 2, 4, 3]
-# Remove from the end with pop
-li.pop()  # => 3 and li is now [1, 2, 4]
-# Let's put it back
-li.append(3)  # li is now [1, 2, 4, 3] again.
+# Add stuff to the end of a list with append
+li.append(1)    # li is now [1]
+li.append(2)    # li is now [1, 2]
+li.append(4)    # li is now [1, 2, 4]
+li.append(3)    # li is now [1, 2, 4, 3]
+# Remove from the end with pop
+li.pop()        # => 3 and li is now [1, 2, 4]
+# Let's put it back
+li.append(3)    # li is now [1, 2, 4, 3] again.
 
-# Access a list like you would any array
-li[0]  # => 1
-# Assign new values to indexes that have already been initialized with =
-li[0] = 42
-li[0]  # => 42
-li[0] = 1  # Note: setting it back to the original value
-# Look at the last element
-li[-1]  # => 3
+# Access a list like you would any array
+li[0]   # => 1
+# Look at the last element
+li[-1]  # => 3
 
-# Looking out of bounds is an IndexError
-li[4]  # Raises an IndexError
+# Looking out of bounds is an IndexError
+li[4]  # Raises an IndexError
 
-# You can look at ranges with slice syntax.
-# (It's a closed/open range for you mathy types.)
-li[1:3]  # => [2, 4]
-# Omit the beginning
-li[2:]  # => [4, 3]
-# Omit the end
-li[:3]  # => [1, 2, 4]
-# Select every second entry
-li[::2]  # =>[1, 4]
-# Reverse a copy of the list
-li[::-1]  # => [3, 4, 2, 1]
-# Use any combination of these to make advanced slices
-# li[start:end:step]
+# You can look at ranges with slice syntax.
+# The start index is included, the end index is not
+# (It's a closed/open range for you mathy types.)
+li[1:3]   # Return list from index 1 to 3 => [2, 4]
+li[2:]    # Return list starting from index 2 => [4, 3]
+li[:3]    # Return list from beginning until index 3  => [1, 2, 4]
+li[::2]   # Return list selecting every second entry => [1, 4]
+li[::-1]  # Return list in reverse order => [3, 4, 2, 1]
+# Use any combination of these to make advanced slices
+# li[start:end:step]
 
-# Remove arbitrary elements from a list with "del"
-del li[2]  # li is now [1, 2, 3]
+# Make a one layer deep copy using slices
+li2 = li[:]  # => li2 = [1, 2, 4, 3] but (li2 is li) will result in false.
 
-# You can add lists
-li + other_li  # => [1, 2, 3, 4, 5, 6]
-# Note: values for li and for other_li are not modified.
+# Remove arbitrary elements from a list with "del"
+del li[2]  # li is now [1, 2, 3]
 
-# Concatenate lists with "extend()"
-li.extend(other_li)  # Now li is [1, 2, 3, 4, 5, 6]
+# Remove first occurrence of a value
+li.remove(2)  # li is now [1, 3]
+li.remove(2)  # Raises a ValueError as 2 is not in the list
 
-# Remove first occurrence of a value
-li.remove(2)  # li is now [1, 3, 4, 5, 6]
-li.remove(2)  # Raises a ValueError as 2 is not in the list
+# Insert an element at a specific index
+li.insert(1, 2)  # li is now [1, 2, 3] again
 
-# Insert an element at a specific index
-li.insert(1, 2)  # li is now [1, 2, 3, 4, 5, 6] again
+# Get the index of the first item found matching the argument
+li.index(2)  # => 1
+li.index(4)  # Raises a ValueError as 4 is not in the list
 
-# Get the index of the first item found
-li.index(2)  # => 1
-li.index(7)  # Raises a ValueError as 7 is not in the list
+# You can add lists
+# Note: values for li and for other_li are not modified.
+li + other_li  # => [1, 2, 3, 4, 5, 6]
 
-# Check for existence in a list with "in"
-1 in li  # => True
+# Concatenate lists with "extend()"
+li.extend(other_li)  # Now li is [1, 2, 3, 4, 5, 6]
 
-# Examine the length with "len()"
-len(li)  # => 6
+# Check for existence in a list with "in"
+1 in li  # => True
 
-# Tuples are like lists but are immutable.
+# Examine the length with "len()"
+len(li)  # => 6
+
+
+# Tuples are like lists but are immutable.
 tup = (1, 2, 3)
-tup[0]  # => 1
-tup[0] = 3  # Raises a TypeError
+tup[0]      # => 1
+tup[0] = 3  # Raises a TypeError
 
-# You can do all those list thingies on tuples too
-len(tup)  # => 3
-tup + (4, 5, 6)  # => (1, 2, 3, 4, 5, 6)
-tup[:2]  # => (1, 2)
-2 in tup  # => True
+# Note that a tuple of length one has to have a comma after the last element but
+# tuples of other lengths, even zero, do not.
+type((1))   # => <class 'int'>
+type((1,))  # => <class 'tuple'>
+type(())    # => <class 'tuple'>
 
-# You can unpack tuples (or lists) into variables
-a, b, c = (1, 2, 3)  # a is now 1, b is now 2 and c is now 3
-d, e, f = 4, 5, 6  # you can leave out the parentheses
-# Tuples are created by default if you leave out the parentheses
-g = 4, 5, 6  # => (4, 5, 6)
-# Now look how easy it is to swap two values
-e, d = d, e  # d is now 5 and e is now 4
+# You can do most of the list operations on tuples too
+len(tup)         # => 3
+tup + (4, 5, 6)  # => (1, 2, 3, 4, 5, 6)
+tup[:2]          # => (1, 2)
+2 in tup         # => True
 
-# Dictionaries store mappings
+# You can unpack tuples (or lists) into variables
+a, b, c = (1, 2, 3)  # a is now 1, b is now 2 and c is now 3
+# You can also do extended unpacking
+a, *b, c = (1, 2, 3, 4)  # a is now 1, b is now [2, 3] and c is now 4
+# Tuples are created by default if you leave out the parentheses
+d, e, f = 4, 5, 6  # tuple 4, 5, 6 is unpacked into variables d, e and f
+# respectively such that d = 4, e = 5 and f = 6
+# Now look how easy it is to swap two values
+e, d = d, e  # d is now 5 and e is now 4
+
+
+# Dictionaries store mappings from keys to values
 empty_dict = {}
-# Here is a prefilled dictionary
+# Here is a prefilled dictionary
 filled_dict = {"one": 1, "two": 2, "three": 3}
 
-# Look up values with []
-filled_dict["one"]  # => 1
+# Note keys for dictionaries have to be immutable types. This is to ensure that
+# the key can be converted to a constant hash value for quick look-ups.
+# Immutable types include ints, floats, strings, tuples.
+invalid_dict = {[1,2,3]: "123"}  # => Raises a TypeError: unhashable type: 'list'
+valid_dict = {(1,2,3):[1,2,3]}   # Values can be of any type, however.
 
-# Get all keys as a list with "keys()"
-filled_dict.keys()  # => ["three", "two", "one"]
-# Note - Dictionary key ordering is not guaranteed.
-# Your results might not match this exactly.
+# Look up values with []
+filled_dict["one"]  # => 1
 
-# Get all values as a list with "values()"
-filled_dict.values()  # => [3, 2, 1]
-# Note - Same as above regarding key ordering.
+# Get all keys as an iterable with "keys()". We need to wrap the call in list()
+# to turn it into a list. We'll talk about those later.  Note - for Python
+# versions <3.7, dictionary key ordering is not guaranteed. Your results might
+# not match the example below exactly. However, as of Python 3.7, dictionary
+# items maintain the order at which they are inserted into the dictionary.
+list(filled_dict.keys())  # => ["three", "two", "one"] in Python <3.7
+list(filled_dict.keys())  # => ["one", "two", "three"] in Python 3.7+
 
-# Get all key-value pairs as a list of tuples with "items()"
-filled_dict.items()  # => [("one", 1), ("two", 2), ("three", 3)]
 
-# Check for existence of keys in a dictionary with "in"
-"one" in filled_dict  # => True
-1 in filled_dict  # => False
+# Get all values as an iterable with "values()". Once again we need to wrap it
+# in list() to get it out of the iterable. Note - Same as above regarding key
+# ordering.
+list(filled_dict.values())  # => [3, 2, 1]  in Python <3.7
+list(filled_dict.values())  # => [1, 2, 3] in Python 3.7+
 
-# Looking up a non-existing key is a KeyError
-filled_dict["four"]  # KeyError
+# Check for existence of keys in a dictionary with "in"
+"one" in filled_dict  # => True
+1 in filled_dict      # => False
 
-# Use "get()" method to avoid the KeyError
-filled_dict.get("one")  # => 1
-filled_dict.get("four")  # => None
-# The get method supports a default argument when the value is missing
-filled_dict.get("one", 4)  # => 1
-filled_dict.get("four", 4)  # => 4
-# note that filled_dict.get("four") is still => None
-# (get doesn't set the value in the dictionary)
+# Looking up a non-existing key is a KeyError
+filled_dict["four"]  # KeyError
 
-# set the value of a key with a syntax similar to lists
-filled_dict["four"] = 4  # now, filled_dict["four"] => 4
+# Use "get()" method to avoid the KeyError
+filled_dict.get("one")      # => 1
+filled_dict.get("four")     # => None
+# The get method supports a default argument when the value is missing
+filled_dict.get("one", 4)   # => 1
+filled_dict.get("four", 4)  # => 4
 
-# "setdefault()" inserts into a dictionary only if the given key isn't present
-filled_dict.setdefault("five", 5)  # filled_dict["five"] is set to 5
-filled_dict.setdefault("five", 6)  # filled_dict["five"] is still 5
+# "setdefault()" inserts into a dictionary only if the given key isn't present
+filled_dict.setdefault("five", 5)  # filled_dict["five"] is set to 5
+filled_dict.setdefault("five", 6)  # filled_dict["five"] is still 5
 
-# You can declare sets (which are like unordered lists that cannot contain
-# duplicate values) using the set object.
+# Adding to a dictionary
+filled_dict.update({"four":4})  # => {"one": 1, "two": 2, "three": 3, "four": 4}
+filled_dict["four"] = 4         # another way to add to dict
+
+# Remove keys from a dictionary with del
+del filled_dict["one"]  # Removes the key "one" from filled dict
+
+# From Python 3.5 you can also use the additional unpacking options
+{'a': 1, **{'b': 2}}  # => {'a': 1, 'b': 2}
+{'a': 1, **{'a': 2}}  # => {'a': 2}
+
+
+
+# Sets store ... well sets
 empty_set = set()
-# Initialize a "set()" with a bunch of values
-some_set = set([1, 2, 2, 3, 4])  # some_set is now set([1, 2, 3, 4])
+# Initialize a set with a bunch of values. Yeah, it looks a bit like a dict. Sorry.
+some_set = {1, 1, 2, 2, 3, 4}  # some_set is now {1, 2, 3, 4}
 
-# order is not guaranteed, even though it may sometimes look sorted
-another_set = set([4, 3, 2, 2, 1])  # another_set is now set([1, 2, 3, 4])
+# Similar to keys of a dictionary, elements of a set have to be immutable.
+invalid_set = {[1], 1}  # => Raises a TypeError: unhashable type: 'list'
+valid_set = {(1,), 1}
 
-# Since Python 2.7, {} can be used to declare a set
-filled_set = {1, 2, 2, 3, 4}  # => {1, 2, 3, 4}
+# Add one more item to the set
+filled_set = some_set
+filled_set.add(5)  # filled_set is now {1, 2, 3, 4, 5}
+# Sets do not have duplicate elements
+filled_set.add(5)  # it remains as before {1, 2, 3, 4, 5}
 
-# Add more items to a set
-filled_set.add(5)  # filled_set is now {1, 2, 3, 4, 5}
-
-# Do set intersection with &
+# Do set intersection with &
 other_set = {3, 4, 5, 6}
-filled_set & other_set  # => {3, 4, 5}
+filled_set & other_set  # => {3, 4, 5}
 
-# Do set union with |
-filled_set | other_set  # => {1, 2, 3, 4, 5, 6}
+# Do set union with |
+filled_set | other_set  # => {1, 2, 3, 4, 5, 6}
 
-# Do set difference with -
-{1, 2, 3, 4} - {2, 3, 5}  # => {1, 4}
+# Do set difference with -
+{1, 2, 3, 4} - {2, 3, 5}  # => {1, 4}
 
-# Do set symmetric difference with ^
-{1, 2, 3, 4} ^ {2, 3, 5}  # => {1, 4, 5}
+# Do set symmetric difference with ^
+{1, 2, 3, 4} ^ {2, 3, 5}  # => {1, 4, 5}
 
-# Check if set on the left is a superset of set on the right
-{1, 2} >= {1, 2, 3}  # => False
+# Check if set on the left is a superset of set on the right
+{1, 2} >= {1, 2, 3} # => False
 
-# Check if set on the left is a subset of set on the right
-{1, 2} <= {1, 2, 3}  # => True
+# Check if set on the left is a subset of set on the right
+{1, 2} <= {1, 2, 3} # => True
 
-# Check for existence in a set with in
-2 in filled_set  # => True
-10 in filled_set  # => False
-10 not in filled_set # => True
+# Check for existence in a set with in
+2 in filled_set   # => True
+10 in filled_set  # => False
 
-# Check data type of variable
-type(li)   # => list
-type(filled_dict)   # => dict
-type(5)   # => int
+# Make a one layer deep copy
+filled_set = some_set.copy()  # filled_set is {1, 2, 3, 4, 5}
+filled_set is some_set        # => False
 
 
-####################################################
-#  3. Control Flow
-####################################################
+####################################################
+## 3. Control Flow and Iterables
+####################################################
 
-# Let's just make a variable
+# Let's just make a variable
 some_var = 5
 
-# Here is an if statement. Indentation is significant in python!
-# prints "some_var is smaller than 10"
+# Here is an if statement. Indentation is significant in Python!
+# Convention is to use four spaces, not tabs.
+# This prints "some_var is smaller than 10"
 if some_var > 10:
-    print "some_var is totally bigger than 10."
-elif some_var < 10:  # This elif clause is optional.
-    print "some_var is smaller than 10."
-else:  # This is optional too.
-    print "some_var is indeed 10."
+    print("some_var is totally bigger than 10.")
+elif some_var < 10:    # This elif clause is optional.
+    print("some_var is smaller than 10.")
+else:                  # This is optional too.
+    print("some_var is indeed 10.")
+
 
 """
 For loops iterate over lists
@@ -365,11 +388,11 @@
     mouse is a mammal
 """
 for animal in ["dog", "cat", "mouse"]:
-    # You can use {0} to interpolate formatted strings. (See above.)
-    print "{0} is a mammal".format(animal)
+    # You can use format() to interpolate formatted strings
+    print("{} is a mammal".format(animal))
 
 """
-"range(number)" returns a list of numbers
+"range(number)" returns an iterable of numbers
 from zero to the given number
 prints:
     0
@@ -378,10 +401,10 @@
     3
 """
 for i in range(4):
-    print i
+    print(i)
 
 """
-"range(lower, upper)" returns a list of numbers
+"range(lower, upper)" returns an iterable of numbers
 from the lower number to the upper number
 prints:
     4
@@ -390,7 +413,29 @@
     7
 """
 for i in range(4, 8):
-    print i
+    print(i)
+
+"""
+"range(lower, upper, step)" returns an iterable of numbers
+from the lower number to the upper number, while incrementing
+by step. If step is not indicated, the default value is 1.
+prints:
+    4
+    6
+"""
+for i in range(4, 8, 2):
+    print(i)
+
+"""
+To loop over a list, and retrieve both the index and the value of each item in the list
+prints:
+    0 dog
+    1 cat
+    2 mouse
+"""
+animals = ["dog", "cat", "mouse"]
+for i, value in enumerate(animals):
+    print(i, value)
 
 """
 While loops go until a condition is no longer met.
@@ -402,353 +447,537 @@
 """
 x = 0
 while x < 4:
-    print x
-    x += 1  # Shorthand for x = x + 1
+    print(x)
+    x += 1  # Shorthand for x = x + 1
 
-# Handle exceptions with a try/except block
-
-# Works on Python 2.6 and up:
+# Handle exceptions with a try/except block
 try:
-    # Use "raise" to raise an error
+    # Use "raise" to raise an error
     raise IndexError("This is an index error")
 except IndexError as e:
-    pass  # Pass is just a no-op. Usually you would do recovery here.
+    pass                 # Pass is just a no-op. Usually you would do recovery here.
 except (TypeError, NameError):
-    pass  # Multiple exceptions can be handled together, if required.
-else:  # Optional clause to the try/except block. Must follow all except blocks
-    print "All good!"  # Runs only if the code in try raises no exceptions
-finally:  # Execute under all circumstances
-    print "We can clean up resources here"
+    pass                 # Multiple exceptions can be handled together, if required.
+else:                    # Optional clause to the try/except block. Must follow all except blocks
+    print("All good!")   # Runs only if the code in try raises no exceptions
+finally:                 #  Execute under all circumstances
+    print("We can clean up resources here")
 
-# Instead of try/finally to cleanup resources you can use a with statement
+# Instead of try/finally to cleanup resources you can use a with statement
 with open("myfile.txt") as f:
     for line in f:
-        print line
+        print(line)
+
+# Writing to a file
+contents = {"aa": 12, "bb": 21}
+with open("myfile1.txt", "w+") as file:
+    file.write(str(contents))        # writes a string to a file
+
+with open("myfile2.txt", "w+") as file:
+    file.write(json.dumps(contents)) # writes an object to a file
+
+# Reading from a file
+with open('myfile1.txt', "r+") as file:
+    contents = file.read()           # reads a string from a file
+print(contents)
+# print: {"aa": 12, "bb": 21}
+
+with open('myfile2.txt', "r+") as file:
+    contents = json.load(file)       # reads a json object from a file
+print(contents)     
+# print: {"aa": 12, "bb": 21}
 
 
-####################################################
-# 4. Functions
-####################################################
+# Python offers a fundamental abstraction called the Iterable.
+# An iterable is an object that can be treated as a sequence.
+# The object returned by the range function, is an iterable.
 
-# Use "def" to create new functions
+filled_dict = {"one": 1, "two": 2, "three": 3}
+our_iterable = filled_dict.keys()
+print(our_iterable)  # => dict_keys(['one', 'two', 'three']). This is an object that implements our Iterable interface.
+
+# We can loop over it.
+for i in our_iterable:
+    print(i)  # Prints one, two, three
+
+# However we cannot address elements by index.
+our_iterable[1]  # Raises a TypeError
+
+# An iterable is an object that knows how to create an iterator.
+our_iterator = iter(our_iterable)
+
+# Our iterator is an object that can remember the state as we traverse through it.
+# We get the next object with "next()".
+next(our_iterator)  # => "one"
+
+# It maintains state as we iterate.
+next(our_iterator)  # => "two"
+next(our_iterator)  # => "three"
+
+# After the iterator has returned all of its data, it raises a StopIteration exception
+next(our_iterator)  # Raises StopIteration
+
+# We can also loop over it, in fact, "for" does this implicitly!
+our_iterator = iter(our_iterable)
+for i in our_iterator:
+    print(i)  # Prints one, two, three
+
+# You can grab all the elements of an iterable or iterator by calling list() on it.
+list(our_iterable)  # => Returns ["one", "two", "three"]
+list(our_iterator)  # => Returns [] because state is saved
+
+
+####################################################
+## 4. Functions
+####################################################
+
+# Use "def" to create new functions
 def add(x, y):
-    print "x is {0} and y is {1}".format(x, y)
-    return x + y  # Return values with a return statement
+    print("x is {} and y is {}".format(x, y))
+    return x + y  # Return values with a return statement
 
+# Calling functions with parameters
+add(5, 6)  # => prints out "x is 5 and y is 6" and returns 11
 
-# Calling functions with parameters
-add(5, 6)  # => prints out "x is 5 and y is 6" and returns 11
+# Another way to call functions is with keyword arguments
+add(y=6, x=5)  # Keyword arguments can arrive in any order.
 
-# Another way to call functions is with keyword arguments
-add(y=6, x=5)  # Keyword arguments can arrive in any order.
-
-
-# You can define functions that take a variable number of
-# positional args, which will be interpreted as a tuple by using *
+# You can define functions that take a variable number of
+# positional arguments
 def varargs(*args):
     return args
 
+varargs(1, 2, 3)  # => (1, 2, 3)
 
-varargs(1, 2, 3)  # => (1, 2, 3)
-
-
-# You can define functions that take a variable number of
-# keyword args, as well, which will be interpreted as a dict by using **
+# You can define functions that take a variable number of
+# keyword arguments, as well
 def keyword_args(**kwargs):
     return kwargs
 
-
-# Let's call it to see what happens
-keyword_args(big="foot", loch="ness")  # => {"big": "foot", "loch": "ness"}
+# Let's call it to see what happens
+keyword_args(big="foot", loch="ness")  # => {"big": "foot", "loch": "ness"}
 
 
-# You can do both at once, if you like
+# You can do both at once, if you like
 def all_the_args(*args, **kwargs):
-    print args
-    print kwargs
-
-
+    print(args)
+    print(kwargs)
 """
 all_the_args(1, 2, a=3, b=4) prints:
     (1, 2)
     {"a": 3, "b": 4}
 """
 
-# When calling functions, you can do the opposite of args/kwargs!
-# Use * to expand positional args and use ** to expand keyword args.
+# When calling functions, you can do the opposite of args/kwargs!
+# Use * to expand tuples and use ** to expand kwargs.
 args = (1, 2, 3, 4)
 kwargs = {"a": 3, "b": 4}
-all_the_args(*args)  # equivalent to all_the_args(1, 2, 3, 4)
-all_the_args(**kwargs)  # equivalent to all_the_args(a=3, b=4)
-all_the_args(*args, **kwargs)  # equivalent to all_the_args(1, 2, 3, 4, a=3, b=4)
+all_the_args(*args)            # equivalent to all_the_args(1, 2, 3, 4)
+all_the_args(**kwargs)         # equivalent to all_the_args(a=3, b=4)
+all_the_args(*args, **kwargs)  # equivalent to all_the_args(1, 2, 3, 4, a=3, b=4)
 
+# Returning multiple values (with tuple assignments)
+def swap(x, y):
+    return y, x  # Return multiple values as a tuple without the parenthesis.
+                 # (Note: parenthesis have been excluded but can be included)
 
-# you can pass args and kwargs along to other functions that take args/kwargs
-# by expanding them with * and ** respectively
-def pass_all_the_args(*args, **kwargs):
-    all_the_args(*args, **kwargs)
-    print varargs(*args)
-    print keyword_args(**kwargs)
+x = 1
+y = 2
+x, y = swap(x, y)     # => x = 2, y = 1
+# (x, y) = swap(x,y)  # Again parenthesis have been excluded but can be included.
 
-
-# Function Scope
+# Function Scope
 x = 5
 
-
 def set_x(num):
-    # Local var x not the same as global variable x
-    x = num  # => 43
-    print x  # => 43
-
+    # Local var x not the same as global variable x
+    x = num    # => 43
+    print(x)   # => 43
 
 def set_global_x(num):
     global x
-    print x  # => 5
-    x = num  # global var x is now set to 6
-    print x  # => 6
-
+    print(x)   # => 5
+    x = num    # global var x is now set to 6
+    print(x)   # => 6
 
 set_x(43)
 set_global_x(6)
 
 
-# Python has first class functions
+# Python has first class functions
 def create_adder(x):
     def adder(y):
         return x + y
-
     return adder
 
-
 add_10 = create_adder(10)
-add_10(3)  # => 13
+add_10(3)   # => 13
 
-# There are also anonymous functions
-(lambda x: x > 2)(3)  # => True
-(lambda x, y: x ** 2 + y ** 2)(2, 1)  # => 5
+# There are also anonymous functions
+(lambda x: x > 2)(3)                  # => True
+(lambda x, y: x ** 2 + y ** 2)(2, 1)  # => 5
 
-# There are built-in higher order functions
-map(add_10, [1, 2, 3])  # => [11, 12, 13]
-map(max, [1, 2, 3], [4, 2, 1])  # => [4, 2, 3]
+# There are built-in higher order functions
+list(map(add_10, [1, 2, 3]))          # => [11, 12, 13]
+list(map(max, [1, 2, 3], [4, 2, 1]))  # => [4, 2, 3]
 
-filter(lambda x: x > 5, [3, 4, 5, 6, 7])  # => [6, 7]
+list(filter(lambda x: x > 5, [3, 4, 5, 6, 7]))  # => [6, 7]
 
-# We can use list comprehensions for nice maps and filters
-[add_10(i) for i in [1, 2, 3]]  # => [11, 12, 13]
-[x for x in [3, 4, 5, 6, 7] if x > 5]  # => [6, 7]
+# We can use list comprehensions for nice maps and filters
+# List comprehension stores the output as a list which can itself be a nested list
+[add_10(i) for i in [1, 2, 3]]         # => [11, 12, 13]
+[x for x in [3, 4, 5, 6, 7] if x > 5]  # => [6, 7]
 
-# You can construct set and dict comprehensions as well.
-{x for x in 'abcddeef' if x in 'abc'}  # => {'a', 'b', 'c'}
-{x: x ** 2 for x in range(5)}  # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}
+# You can construct set and dict comprehensions as well.
+{x for x in 'abcddeef' if x not in 'abc'}  # => {'d', 'e', 'f'}
+{x: x**2 for x in range(5)}  # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}
 
 
-####################################################
-# 5. Classes
-####################################################
+####################################################
+## 5. Modules
+####################################################
 
-# We subclass from object to get a class.
-class Human(object):
-    # A class attribute. It is shared by all instances of this class
+# You can import modules
+import math
+print(math.sqrt(16))  # => 4.0
+
+# You can get specific functions from a module
+from math import ceil, floor
+print(ceil(3.7))   # => 4.0
+print(floor(3.7))  # => 3.0
+
+# You can import all functions from a module.
+# Warning: this is not recommended
+from math import *
+
+# You can shorten module names
+import math as m
+math.sqrt(16) == m.sqrt(16)  # => True
+
+# Python modules are just ordinary Python files. You
+# can write your own, and import them. The name of the
+# module is the same as the name of the file.
+
+# You can find out which functions and attributes
+# are defined in a module.
+import math
+dir(math)
+
+# If you have a Python script named math.py in the same
+# folder as your current script, the file math.py will
+# be loaded instead of the built-in Python module.
+# This happens because the local folder has priority
+# over Python's built-in libraries.
+
+
+####################################################
+## 6. Classes
+####################################################
+
+# We use the "class" statement to create a class
+class Human:
+
+    # A class attribute. It is shared by all instances of this class
     species = "H. sapiens"
 
-    # Basic initializer, this is called when this class is instantiated.
-    # Note that the double leading and trailing underscores denote objects
-    # or attributes that are used by python but that live in user-controlled
-    # namespaces. You should not invent such names on your own.
+    # Basic initializer, this is called when this class is instantiated.
+    # Note that the double leading and trailing underscores denote objects
+    # or attributes that are used by Python but that live in user-controlled
+    # namespaces. Methods(or objects or attributes) like: __init__, __str__,
+    # __repr__ etc. are called special methods (or sometimes called dunder methods)
+    # You should not invent such names on your own.
     def __init__(self, name):
-        # Assign the argument to the instance's name attribute
+        # Assign the argument to the instance's name attribute
         self.name = name
 
-        # Initialize property
-        self.age = 0
+        # Initialize property
+        self._age = 0
 
-    # An instance method. All methods take "self" as the first argument
+    # An instance method. All methods take "self" as the first argument
     def say(self, msg):
-        return "{0}: {1}".format(self.name, msg)
+        print("{name}: {message}".format(name=self.name, message=msg))
 
-    # A class method is shared among all instances
-    # They are called with the calling class as the first argument
+    # Another instance method
+    def sing(self):
+        return 'yo... yo... microphone check... one two... one two...'
+
+    # A class method is shared among all instances
+    # They are called with the calling class as the first argument
     @classmethod
     def get_species(cls):
         return cls.species
 
-    # A static method is called without a class or instance reference
+    # A static method is called without a class or instance reference
     @staticmethod
     def grunt():
         return "*grunt*"
 
-    # A property is just like a getter.
-    # It turns the method age() into an read-only attribute
-    # of the same name.
+    # A property is just like a getter.
+    # It turns the method age() into an read-only attribute of the same name.
+    # There's no need to write trivial getters and setters in Python, though.
     @property
     def age(self):
         return self._age
 
-    # This allows the property to be set
-    @age.setter
+    # This allows the property to be set
+    @age.setter
     def age(self, age):
         self._age = age
 
-    # This allows the property to be deleted
-    @age.deleter
+    # This allows the property to be deleted
+    @age.deleter
     def age(self):
         del self._age
 
 
-# Instantiate a class
-i = Human(name="Ian")
-print i.say("hi")  # prints out "Ian: hi"
+# When a Python interpreter reads a source file it executes all its code.
+# This __name__ check makes sure this code block is only executed when this
+# module is the main program.
+if __name__ == '__main__':
+    # Instantiate a class
+    i = Human(name="Ian")
+    i.say("hi")                     # "Ian: hi"
+    j = Human("Joel")
+    j.say("hello")                  # "Joel: hello"
+    # i and j are instances of type Human, or in other words: they are Human objects
 
-j = Human("Joel")
-print j.say("hello")  # prints out "Joel: hello"
+    # Call our class method
+    i.say(i.get_species())          # "Ian: H. sapiens"
+    # Change the shared attribute
+    Human.species = "H. neanderthalensis"
+    i.say(i.get_species())          # => "Ian: H. neanderthalensis"
+    j.say(j.get_species())          # => "Joel: H. neanderthalensis"
 
-# Call our class method
-i.get_species()  # => "H. sapiens"
+    # Call the static method
+    print(Human.grunt())            # => "*grunt*"
 
-# Change the shared attribute
-Human.species = "H. neanderthalensis"
-i.get_species()  # => "H. neanderthalensis"
-j.get_species()  # => "H. neanderthalensis"
+    # Cannot call static method with instance of object
+    # because i.grunt() will automatically put "self" (the object i) as an argument
+    print(i.grunt())                # => TypeError: grunt() takes 0 positional arguments but 1 was given
 
-# Call the static method
-Human.grunt()  # => "*grunt*"
-
-# Update the property
-i.age = 42
-
-# Get the property
-i.age  # => 42
-
-# Delete the property
-del i.age
-i.age  # => raises an AttributeError
-
-####################################################
-# 6. Modules
-####################################################
-
-# You can import modules
-import math
-
-print math.sqrt(16)  # => 4.0
-
-# You can get specific functions from a module
-from math import ceil, floor
-
-print ceil(3.7)  # => 4.0
-print floor(3.7)  # => 3.0
-
-# You can import all functions from a module.
-# Warning: this is not recommended
-from math import *
-
-# You can shorten module names
-import math as m
-
-math.sqrt(16) == m.sqrt(16)  # => True
-# you can also test that the functions are equivalent
-from math import sqrt
-
-math.sqrt == m.sqrt == sqrt  # => True
-
-# Python modules are just ordinary python files. You
-# can write your own, and import them. The name of the
-# module is the same as the name of the file.
-
-# You can find out which functions and attributes
-# defines a module.
-import math
-
-dir(math)
+    # Update the property for this instance
+    i.age = 42
+    # Get the property
+    i.say(i.age)                    # => "Ian: 42"
+    j.say(j.age)                    # => "Joel: 0"
+    # Delete the property
+    del i.age
+    # i.age                         # => this would raise an AttributeError
 
 
-# If you have a Python script named math.py in the same
-# folder as your current script, the file math.py will
-# be loaded instead of the built-in Python module.
-# This happens because the local folder has priority
-# over Python's built-in libraries.
+####################################################
+## 6.1 Inheritance
+####################################################
+
+# Inheritance allows new child classes to be defined that inherit methods and
+# variables from their parent class.
+
+# Using the Human class defined above as the base or parent class, we can
+# define a child class, Superhero, which inherits the class variables like
+# "species", "name", and "age", as well as methods, like "sing" and "grunt"
+# from the Human class, but can also have its own unique properties.
+
+# To take advantage of modularization by file you could place the classes above in their own files,
+# say, human.py
+
+# To import functions from other files use the following format
+# from "filename-without-extension" import "function-or-class"
+
+from human import Human
 
 
-####################################################
-# 7. Advanced
-####################################################
+# Specify the parent class(es) as parameters to the class definition
+class Superhero(Human):
 
-# Generators
-# A generator "generates" values as they are requested instead of storing
-# everything up front
+    # If the child class should inherit all of the parent's definitions without
+    # any modifications, you can just use the "pass" keyword (and nothing else)
+    # but in this case it is commented out to allow for a unique child class:
+    # pass
 
-# The following method (*NOT* a generator) will double all values and store it
-# in `double_arr`. For large size of iterables, that might get huge!
+    # Child classes can override their parents' attributes
+    species = 'Superhuman'
+
+    # Children automatically inherit their parent class's constructor including
+    # its arguments, but can also define additional arguments or definitions
+    # and override its methods such as the class constructor.
+    # This constructor inherits the "name" argument from the "Human" class and
+    # adds the "superpower" and "movie" arguments:
+    def __init__(self, name, movie=False,
+                 superpowers=["super strength", "bulletproofing"]):
+
+        # add additional class attributes:
+        self.fictional = True
+        self.movie = movie
+        # be aware of mutable default values, since defaults are shared
+        self.superpowers = superpowers
+
+        # The "super" function lets you access the parent class's methods
+        # that are overridden by the child, in this case, the __init__ method.
+        # This calls the parent class constructor:
+        super().__init__(name)
+
+    # override the sing method
+    def sing(self):
+        return 'Dun, dun, DUN!'
+
+    # add an additional instance method
+    def boast(self):
+        for power in self.superpowers:
+            print("I wield the power of {pow}!".format(pow=power))
+
+
+if __name__ == '__main__':
+    sup = Superhero(name="Tick")
+
+    # Instance type checks
+    if isinstance(sup, Human):
+        print('I am human')
+    if type(sup) is Superhero:
+        print('I am a superhero')
+
+    # Get the Method Resolution search Order used by both getattr() and super()
+    # This attribute is dynamic and can be updated
+    print(Superhero.__mro__)    # => (<class '__main__.Superhero'>,
+                                # => <class 'human.Human'>, <class 'object'>)
+
+    # Calls parent method but uses its own class attribute
+    print(sup.get_species())    # => Superhuman
+
+    # Calls overridden method
+    print(sup.sing())           # => Dun, dun, DUN!
+
+    # Calls method from Human
+    sup.say('Spoon')            # => Tick: Spoon
+
+    # Call method that exists only in Superhero
+    sup.boast()                 # => I wield the power of super strength!
+                                # => I wield the power of bulletproofing!
+
+    # Inherited class attribute
+    sup.age = 31
+    print(sup.age)              # => 31
+
+    # Attribute that only exists within Superhero
+    print('Am I Oscar eligible? ' + str(sup.movie))
+
+####################################################
+## 6.2 Multiple Inheritance
+####################################################
+
+# Another class definition
+# bat.py
+class Bat:
+
+    species = 'Baty'
+
+    def __init__(self, can_fly=True):
+        self.fly = can_fly
+
+    # This class also has a say method
+    def say(self, msg):
+        msg = '... ... ...'
+        return msg
+
+    # And its own method as well
+    def sonar(self):
+        return '))) ... ((('
+
+if __name__ == '__main__':
+    b = Bat()
+    print(b.say('hello'))
+    print(b.fly)
+
+
+# And yet another class definition that inherits from Superhero and Bat
+# superhero.py
+from superhero import Superhero
+from bat import Bat
+
+# Define Batman as a child that inherits from both Superhero and Bat
+class Batman(Superhero, Bat):
+
+    def __init__(self, *args, **kwargs):
+        # Typically to inherit attributes you have to call super:
+        # super(Batman, self).__init__(*args, **kwargs)      
+        # However we are dealing with multiple inheritance here, and super()
+        # only works with the next base class in the MRO list.
+        # So instead we explicitly call __init__ for all ancestors.
+        # The use of *args and **kwargs allows for a clean way to pass arguments,
+        # with each parent "peeling a layer of the onion".
+        Superhero.__init__(self, 'anonymous', movie=True,
+                           superpowers=['Wealthy'], *args, **kwargs)
+        Bat.__init__(self, *args, can_fly=False, **kwargs)
+        # override the value for the name attribute
+        self.name = 'Sad Affleck'
+
+    def sing(self):
+        return 'nan nan nan nan nan batman!'
+
+
+if __name__ == '__main__':
+    sup = Batman()
+
+    # Get the Method Resolution search Order used by both getattr() and super().
+    # This attribute is dynamic and can be updated
+    print(Batman.__mro__)       # => (<class '__main__.Batman'>,
+                                # => <class 'superhero.Superhero'>,
+                                # => <class 'human.Human'>,
+                                # => <class 'bat.Bat'>, <class 'object'>)
+
+    # Calls parent method but uses its own class attribute
+    print(sup.get_species())    # => Superhuman
+
+    # Calls overridden method
+    print(sup.sing())           # => nan nan nan nan nan batman!
+
+    # Calls method from Human, because inheritance order matters
+    sup.say('I agree')          # => Sad Affleck: I agree
+
+    # Call method that exists only in 2nd ancestor
+    print(sup.sonar())          # => ))) ... (((
+
+    # Inherited class attribute
+    sup.age = 100
+    print(sup.age)              # => 100
+
+    # Inherited attribute from 2nd ancestor whose default value was overridden.
+    print('Can I fly? ' + str(sup.fly)) # => Can I fly? False
+
+
+
+####################################################
+## 7. Advanced
+####################################################
+
+# Generators help you make lazy code.
 def double_numbers(iterable):
-    double_arr = []
-    for i in iterable:
-        double_arr.append(i + i)
-    return double_arr
-
-
-# Running the following would mean we'll double all values first and return all
-# of them back to be checked by our condition
-for value in double_numbers(range(1000000)):  # `test_non_generator`
-    print value
-    if value > 5:
-        break
-
-
-# We could instead use a generator to "generate" the doubled value as the item
-# is being requested
-def double_numbers_generator(iterable):
     for i in iterable:
         yield i + i
 
-
-# Running the same code as before, but with a generator, now allows us to iterate
-# over the values and doubling them one by one as they are being consumed by
-# our logic. Hence as soon as we see a value > 5, we break out of the
-# loop and don't need to double most of the values sent in (MUCH FASTER!)
-for value in double_numbers_generator(xrange(1000000)):  # `test_generator`
-    print value
-    if value > 5:
+# Generators are memory-efficient because they only load the data needed to
+# process the next value in the iterable. This allows them to perform
+# operations on otherwise prohibitively large value ranges.
+# NOTE: `range` replaces `xrange` in Python 3.
+for i in double_numbers(range(1, 900000000)):  # `range` is a generator.
+    print(i)
+    if i >= 30:
         break
 
-# BTW: did you notice the use of `range` in `test_non_generator` and `xrange` in `test_generator`?
-# Just as `double_numbers_generator` is the generator version of `double_numbers`
-# We have `xrange` as the generator version of `range`
-# `range` would return back and array with 1000000 values for us to use
-# `xrange` would generate 1000000 values for us as we request / iterate over those items
-
-# Just as you can create a list comprehension, you can create generator
-# comprehensions as well.
-values = (-x for x in [1, 2, 3, 4, 5])
+# Just as you can create a list comprehension, you can create generator
+# comprehensions as well.
+values = (-x for x in [1,2,3,4,5])
 for x in values:
-    print(x)  # prints -1 -2 -3 -4 -5 to console/terminal
+    print(x)  # prints -1 -2 -3 -4 -5 to console/terminal
 
-# You can also cast a generator comprehension directly to a list.
-values = (-x for x in [1, 2, 3, 4, 5])
+# You can also cast a generator comprehension directly to a list.
+values = (-x for x in [1,2,3,4,5])
 gen_to_list = list(values)
-print(gen_to_list)  # => [-1, -2, -3, -4, -5]
+print(gen_to_list)  # => [-1, -2, -3, -4, -5]
 
-# Decorators
-# A decorator is a higher order function, which accepts and returns a function.
-# Simple usage example – add_apples decorator will add 'Apple' element into
-# fruits list returned by get_fruits target function.
-def add_apples(func):
-    def get_fruits():
-        fruits = func()
-        fruits.append('Apple')
-        return fruits
-    return get_fruits
 
-@add_apples
-def get_fruits():
-    return ['Banana', 'Mango', 'Orange']
-
-# Prints out the list of fruits with 'Apple' element in it:
-# Banana, Mango, Orange, Apple
-print ', '.join(get_fruits())
-
-# in this example beg wraps say
-# Beg will call say. If say_please is True then it will change the returned
-# message
+# Decorators
+# In this example `beg` wraps `say`. If say_please is True then it
+# will change the returned message.
 from functools import wraps
 
 
@@ -757,17 +986,17 @@
     def wrapper(*args, **kwargs):
         msg, say_please = target_function(*args, **kwargs)
         if say_please:
-            return "{} {}".format(msg, "Please! I am poor :(")
+            return "{} {}".format(msg, "Please! I am poor :(")
         return msg
 
     return wrapper
 
 
 @beg
-def say(say_please=False):
+def say(say_please=False):
     msg = "Can you buy me a beer?"
     return msg, say_please
 
 
-print say()  # Can you buy me a beer?
-print say(say_please=True)  # Can you buy me a beer? Please! I am poor :(
+print(say())                 # Can you buy me a beer?
+print(say(say_please=True))  # Can you buy me a beer? Please! I am poor :(
diff --git a/tests/results/16 b/tests/results/16
index ea42750..e33fd7f 100644
--- a/tests/results/16
+++ b/tests/results/16
@@ -2,15 +2,15 @@
 
 1ns                          Main memory reference:       Send 2,000 bytes             Read 1,000,000 bytes         
 ▗▖                           100ns                        over commodity network:      sequentially from SSD:       
-                             ▗▖                           62ns                         61.712us                     
+                             ▗▖                           44ns                         48.981us                     
 L1 cache reference: 1ns                                   ▗                            ▗                            
 ▗▖                           1.0us                                                                                  
-                             ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         SSD random read: 16.0us      Disk seek: 2.679433ms        
-Branch mispredict: 3ns                                    ▗▖▗                          ▗▖▗▖▗                        
+                             ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         SSD random read: 16.0us      Disk seek: 2.499999ms        
+Branch mispredict: 3ns                                    ▗▖▗                          ▗▖▗▖                         
 ▗▖▗▖▗▖                                                                                                              
-                             Compress 1KB with Snappy:     Read 1,000,000 bytes         Read 1,000,000 bytes         
+                             Compress 1KB wth Snappy:     Read 1,000,000 bytes         Read 1,000,000 bytes         
 L2 cache reference: 4ns      2.0us                        sequentially from memory:    sequentially from disk:      
-▗▖▗▖▗▖▗▖                     ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         3.738us                      947.322us                    
+▗▖▗▖▗▖▗▖                     ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         2.967us                      824.692us                    
                              ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖         ▗                            ▗                            
 Mutex lock/unlock: 16ns                                                                                             
 ▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖▗▖                                      Round trip                   Packet roundtrip             
diff --git a/tests/results/17 b/tests/results/17
index ba45f23..a1cc24f 100644
--- a/tests/results/17
+++ b/tests/results/17
@@ -1,33 +1,33 @@
-# Microsoft Azure CLI 2.0
-# Command-line tools for Azure
+# Microsoft Azure CLI 2.0
+# Command-line tools for Azure
 
-# Install Azure CLI 2.0 with one curl command.
+# Install Azure CLI 2.0 with one curl command.
 curl -L https://aka.ms/InstallAzureCli | bash
 
-# create a resource group named "MyResourceGroup" in the westus2 region of Azure
-az group create -n MyResourceGroup -l westus2 
+# create a resource group named "MyResourceGroup" in the westus2 region of Azure
+az group create -n MyResourceGroup -l westus2
 
-# create a Linux VM using the UbuntuTLS image, with two attached storage disks of 10 GB and 20 GB
+# create a Linux VM using the UbuntuTLS image, with two attached storage disks of 10 GB and 20 GB
 az vm create -n MyLinuxVM -g MyResourceGroup --ssh-key-value $HOME/.ssh/id_rsa.pub --image UbuntuLTS --data-disk-sizes-gb 10 20
 
-# list VMs
+# list VMs
 az vm list --output table
 
-# list only VMs having distinct state
+# list only VMs having distinct state
 az vm list -d --query "[?powerState=='VM running']" --output table
 
-# delete VM (with the name MyLinuxVM in the group MyResourceGroup)
+# delete VM (with the name MyLinuxVM in the group MyResourceGroup)
 az vm delete -g MyResourceGroup -n MyLinuxVM --yes
 
-# Delete all VMs in a resource group
+# Delete all VMs in a resource group
 az vm delete --ids $(az vm list -g MyResourceGroup --query "[].id" -o tsv)
 
-# Create an Image based on a running VM
+# Create an Image based on a running VM
 az vm deallocate -g MyResourceGroup -n MyLinuxVM
 az vm generalize -g MyResourceGroup -n MyLinuxVM
 az image create --resource-group MyResourceGroup --name MyTestImage --source MyLinuxVM
 
-# Running VM based on a VHD
+# Running VM based on a VHD
 az storage blob upload --account-name "${account_name}"  \
    --account-key "${account_key}" --container-name "${container_name}" --type page \
    --file "${file}" --name "${vhd_name}"
@@ -36,55 +36,55 @@
    --name myManagedDisk \
    --source https://${account_name}.blob.core.windows.net/${container_name}/${vhd_name}
 
-# open port
+# open port
 az vm open-port --resource-group MyResourceGroup --name MyLinuxVM --port 443 --priority 899
 
-# Show storage accounts
+# Show storage accounts
 az storage account list --output table
 
-# Show contaniers for an account
+# Show contaniers for an account
 az storage container list --account-name mystorageaccount --output table
 
-# Show blobs in a container
+# Show blobs in a container
 az storage blob list --account-name mystorageaccount --container-name mycontainer  --output table
 
-# list account keys
+# list account keys
 az storage account keys list  --account-name STORAGE_NAME --resource-group RESOURCE_GROUP
 
-# Show own images
+# Show own images
 az image list --output table
 
-# Configure default storage location
+# Configure default storage location
 az configure --defaults location=eastus2
 
-# Show disks
+# Show disks
 az disk list --output table
 
-# Copy blob
+# Copy blob
 az storage blob copy start \
-	--source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
-	--account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
-	--account-name destaccount \
-	--destination-container vms \
-	--destination-blob DESTINATION-blob.vhd
+    --source-uri 'https://md-ldh5nknx2rkz.blob.core.windows.net/jzwuuuzzapn0/abcd?sv=2017-04-17&sr=b&si=68041718-6828-4f5e-9e6e-a1b719975062&sig=XXX' \
+    --account-key XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX== \
+    --account-name destaccount \
+    --destination-container vms \
+    --destination-blob DESTINATION-blob.vhd
 
-# List virtual networks
+# List virtual networks
 az network vnet list --output table
 
-# List virtual networks adapters
+# List virtual networks adapters
 az network nic list --output table
 
-# List public IP addresses used by the VMs
+# List public IP addresses used by the VMs
 az vm list-ip-addresses --output table
 
-# create snapshot
+# create snapshot
 az snapshot create --resource-group IC-EXASOL-001 --source vm1-disk1 -n vm1-snap1
 
-# create SAS url for a snapshot
+# create SAS url for a snapshot
 az snapshot grant-access --resource-group IC-EXASOL-001 --name vm1-snap1 --duration-in-seconds 36000 --query '[accessSas]' -o tsv
 
-# attach disk
+# attach disk
 az vm disk attach --vm-name vm1 -g RESOURCE_GROUP --disk DISK1_ID
 
-# detach disk
+# detach disk
 az vm disk detach --vm-name vm1 -g RESOURCE_GROUP --name DISK1_ID
diff --git a/tests/results/18 b/tests/results/18
index 2822759..651c8c0 100644
--- a/tests/results/18
+++ b/tests/results/18
@@ -1,19 +1,19 @@
 >>> s = 'abcdefgh'
 >>> n, m, char, chars = 2, 3, 'd', 'cd'
->>> # starting from n=2 characters in and m=3 in length;
+>>> # starting from n=2 characters in and m=3 in length;
 >>> s[n-1:n+m-1]
 'bcd'
->>> # starting from n characters in, up to the end of the string;
+>>> # starting from n characters in, up to the end of the string;
 >>> s[n-1:]
 'bcdefgh'
->>> # whole string minus last character;
+>>> # whole string minus last character;
 >>> s[:-1]
 'abcdefg'
->>> # starting from a known character char="d" within the string and of m length;
+>>> # starting from a known character char="d" within the string and of m length;
 >>> indx = s.index(char)
 >>> s[indx:indx+m]
 'def'
->>> # starting from a known substring chars="cd" within the string and of m length.
+>>> # starting from a known substring chars="cd" within the string and of m length.
 >>> indx = s.index(chars)
 >>> s[indx:indx+m]
 'cde'
diff --git a/tests/results/2 b/tests/results/2
index 7b1f52f..3e3ad19 100644
--- a/tests/results/2
+++ b/tests/results/2
@@ -1,17 +1,17 @@
-# Displays everything in the target directory
-ls path/to/the/target/directory
+# To display everything in <dir>, excluding hidden files:
+ls <dir>
 
-# Displays everything including hidden files
-ls -a
+# To display everything in <dir>, including hidden files:
+ls -a <dir>
 
-# Displays all files, along with the size (with unit suffixes) and timestamp
-ls -lh 
+# To display all files, along with the size (with unit suffixes) and timestamp
+ls -lh <dir>
 
-# Display files, sorted by size
-ls -S
+# To display files, sorted by size:
+ls -S <dir>
 
-# Display directories only
-ls -d */
+# To display directories only:
+ls -d */ <dir>
 
-# Display directories only, include hidden
-ls -d .*/ */
+# To display directories only, include hidden:
+ls -d .*/ */ <dir>
diff --git a/tests/results/20 b/tests/results/20
index c48b471..e4a147d 100644
--- a/tests/results/20
+++ b/tests/results/20
@@ -65,7 +65,9 @@ Bitmap-Bresenhams-line-algorithm
 Bitmap-Flood-fill
 Bitmap-Histogram
 Bitmap-Midpoint-circle-algorithm
+Bitmap-PPM-conversion-through-a-pipe
 Bitmap-Read-a-PPM-file
+Bitmap-Read-an-image-through-a-pipe
 Bitmap-Write-a-PPM-file
 Bitwise-IO
 Bitwise-operations
@@ -92,10 +94,12 @@ Casting-out-nines
 Catalan-numbers
 Catalan-numbers-Pascals-triangle
 Catamorphism
+Catmull-Clark-subdivision-surface
 Character-codes
 Chat-server
 Check-Machin-like-formulas
 Check-that-file-exists
+Checkpoint-synchronization
 Chinese-remainder-theorem
 Cholesky-decomposition
 Circles-of-given-radius-through-two-points
@@ -107,6 +111,7 @@ Color-of-a-screen-pixel
 Color-quantization
 Colour-bars-Display
 Colour-pinstripe-Display
+Colour-pinstripe-Printer
 Combinations
 Combinations-and-permutations
 Combinations-with-repetitions
@@ -141,6 +146,7 @@ Day-of-the-week
 Deal-cards-for-FreeCell
 Death-Star
 Deconvolution-1D
+Deconvolution-2D+
 Deepcopy
 Define-a-primitive-data-type
 Delegates
@@ -689,6 +695,7 @@ Variadic-function
 Vector-products
 Verify-distribution-uniformity-Chi-squared-test
 Verify-distribution-uniformity-Naive
+Video-display-modes
 Vigen-re-cipher
 Vigen-re-cipher-Cryptanalysis
 Visualize-a-tree
@@ -715,6 +722,7 @@ Y-combinator
 Yahoo--search-interface
 Yin-and-yang
 Zebra-puzzle
+Zeckendorf-arithmetic
 Zeckendorf-number-representation
 Zero-to-the-zero-power
 Zhang-Suen-thinning-algorithm
diff --git a/tests/results/21 b/tests/results/21
index 47840a1..bfd13d3 100644
--- a/tests/results/21
+++ b/tests/results/21
@@ -1,270 +1,270 @@
-// Single-line comments start with two slashes.
-/* Multiline comments start with slash-star,
-   and end with star-slash */
+// Single-line comments start with two slashes.
+/* Multiline comments start with slash-star,
+   and end with star-slash */
 
-// Statements can be terminated by ;
+// Statements can be terminated by ;
 doStuff();
 
-// ... but they don't have to be, as semicolons are automatically inserted
-// wherever there's a newline, except in certain cases.
+// ... but they don't have to be, as semicolons are automatically inserted
+// wherever there's a newline, except in certain cases.
 doStuff()
 
-// Because those cases can cause unexpected results, we'll keep on using
-// semicolons in this guide.
+// Because those cases can cause unexpected results, we'll keep on using
+// semicolons in this guide.
 
-///////////////////////////////////
-// 1. Numbers, Strings and Operators
+///////////////////////////////////
+// 1. Numbers, Strings and Operators
 
-// JavaScript has one number type (which is a 64-bit IEEE 754 double).
-// Doubles have a 52-bit mantissa, which is enough to store integers
-// up to about 9✕10¹⁵ precisely.
-3; // = 3
-1.5; // = 1.5
+// JavaScript has one number type (which is a 64-bit IEEE 754 double).
+// Doubles have a 52-bit mantissa, which is enough to store integers
+// up to about 9✕10¹⁵ precisely.
+3; // = 3
+1.5; // = 1.5
 
-// Some basic arithmetic works as you'd expect.
-1 + 1; // = 2
-0.1 + 0.2; // = 0.30000000000000004
-8 - 1; // = 7
-10 * 2; // = 20
-35 / 5; // = 7
+// Some basic arithmetic works as you'd expect.
+1 + 1; // = 2
+0.1 + 0.2; // = 0.30000000000000004
+8 - 1; // = 7
+10 * 2; // = 20
+35 / 5; // = 7
 
-// Including uneven division.
-5 / 2; // = 2.5
+// Including uneven division.
+5 / 2; // = 2.5
 
-// And modulo division.
-10 % 2; // = 0
-30 % 4; // = 2
-18.5 % 7; // = 4.5
+// And modulo division.
+10 % 2; // = 0
+30 % 4; // = 2
+18.5 % 7; // = 4.5
 
-// Bitwise operations also work; when you perform a bitwise operation your float
-// is converted to a signed int *up to* 32 bits.
-1 << 2; // = 4
+// Bitwise operations also work; when you perform a bitwise operation your float
+// is converted to a signed int *up to* 32 bits.
+1 << 2; // = 4
 
-// Precedence is enforced with parentheses.
-(1 + 3) * 2; // = 8
+// Precedence is enforced with parentheses.
+(1 + 3) * 2; // = 8
 
-// There are three special not-a-real-number values:
-Infinity; // result of e.g. 1/0
--Infinity; // result of e.g. -1/0
-NaN; // result of e.g. 0/0, stands for 'Not a Number'
+// There are three special not-a-real-number values:
+Infinity; // result of e.g. 1/0
+-Infinity; // result of e.g. -1/0
+NaN; // result of e.g. 0/0, stands for 'Not a Number'
 
-// There's also a boolean type.
+// There's also a boolean type.
 true;
 false;
 
-// Strings are created with ' or ".
+// Strings are created with ' or ".
 'abc';
 "Hello, world";
 
-// Negation uses the ! symbol
-!true; // = false
-!false; // = true
+// Negation uses the ! symbol
+!true; // = false
+!false; // = true
 
-// Equality is ===
-1 === 1; // = true
-2 === 1; // = false
+// Equality is ===
+1 === 1; // = true
+2 === 1; // = false
 
-// Inequality is !==
-1 !== 1; // = false
-2 !== 1; // = true
+// Inequality is !==
+1 !== 1; // = false
+2 !== 1; // = true
 
-// More comparisons
-1 < 10; // = true
-1 > 10; // = false
-2 <= 2; // = true
-2 >= 2; // = true
+// More comparisons
+1 < 10; // = true
+1 > 10; // = false
+2 <= 2; // = true
+2 >= 2; // = true
 
-// Strings are concatenated with +
-"Hello " + "world!"; // = "Hello world!"
+// Strings are concatenated with +
+"Hello " + "world!"; // = "Hello world!"
 
-// ... which works with more than just strings
-"1, 2, " + 3; // = "1, 2, 3"
-"Hello " + ["world", "!"]; // = "Hello world,!"
+// ... which works with more than just strings
+"1, 2, " + 3; // = "1, 2, 3"
+"Hello " + ["world", "!"]; // = "Hello world,!"
 
-// and are compared with < and >
-"a" < "b"; // = true
+// and are compared with < and >
+"a" < "b"; // = true
 
-// Type coercion is performed for comparisons with double equals...
-"5" == 5; // = true
-null == undefined; // = true
+// Type coercion is performed for comparisons with double equals...
+"5" == 5; // = true
+null == undefined; // = true
 
-// ...unless you use ===
-"5" === 5; // = false
-null === undefined; // = false
+// ...unless you use ===
+"5" === 5; // = false
+null === undefined; // = false
 
-// ...which can result in some weird behaviour...
-13 + !0; // 14
-"13" + !0; // '13true'
+// ...which can result in some weird behaviour...
+13 + !0; // 14
+"13" + !0; // '13true'
 
-// You can access characters in a string with `charAt`
-"This is a string".charAt(0);  // = 'T'
+// You can access characters in a string with `charAt`
+"This is a string".charAt(0);  // = 'T'
 
-// ...or use `substring` to get larger pieces.
-"Hello world".substring(0, 5); // = "Hello"
+// ...or use `substring` to get larger pieces.
+"Hello world".substring(0, 5); // = "Hello"
 
-// `length` is a property, so don't use ().
-"Hello".length; // = 5
+// `length` is a property, so don't use ().
+"Hello".length; // = 5
 
-// There's also `null` and `undefined`.
-null;      // used to indicate a deliberate non-value
-undefined; // used to indicate a value is not currently present (although
-           // `undefined` is actually a value itself)
+// There's also `null` and `undefined`.
+null;      // used to indicate a deliberate non-value
+undefined; // used to indicate a value is not currently present (although
+           // `undefined` is actually a value itself)
 
-// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
-// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
+// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
+// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
 
-///////////////////////////////////
-// 2. Variables, Arrays and Objects
+///////////////////////////////////
+// 2. Variables, Arrays and Objects
 
-// Variables are declared with the `var` keyword. JavaScript is dynamically
-// typed, so you don't need to specify type. Assignment uses a single `=`
-// character.
+// Variables are declared with the `var` keyword. JavaScript is dynamically
+// typed, so you don't need to specify type. Assignment uses a single `=`
+// character.
 var someVar = 5;
 
-// If you leave the var keyword off, you won't get an error...
+// If you leave the var keyword off, you won't get an error...
 someOtherVar = 10;
 
-// ...but your variable will be created in the global scope, not in the scope
-// you defined it in.
+// ...but your variable will be created in the global scope, not in the scope
+// you defined it in.
 
-// Variables declared without being assigned to are set to undefined.
-var someThirdVar; // = undefined
+// Variables declared without being assigned to are set to undefined.
+var someThirdVar; // = undefined
 
-// If you want to declare a couple of variables, then you could use a comma
-// separator
+// If you want to declare a couple of variables, then you could use a comma
+// separator
 var someFourthVar = 2, someFifthVar = 4;
 
-// There's shorthand for performing math operations on variables:
-someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
-someVar *= 10; // now someVar is 100
+// There's shorthand for performing math operations on variables:
+someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
+someVar *= 10; // now someVar is 100
 
-// and an even-shorter-hand for adding or subtracting 1
-someVar++; // now someVar is 101
-someVar--; // back to 100
+// and an even-shorter-hand for adding or subtracting 1
+someVar++; // now someVar is 101
+someVar--; // back to 100
 
-// Arrays are ordered lists of values, of any type.
+// Arrays are ordered lists of values, of any type.
 var myArray = ["Hello", 45, true];
 
-// Their members can be accessed using the square-brackets subscript syntax.
-// Array indices start at zero.
-myArray[1]; // = 45
+// Their members can be accessed using the square-brackets subscript syntax.
+// Array indices start at zero.
+myArray[1]; // = 45
 
-// Arrays are mutable and of variable length.
+// Arrays are mutable and of variable length.
 myArray.push("World");
-myArray.length; // = 4
+myArray.length; // = 4
 
-// Add/Modify at specific index
+// Add/Modify at specific index
 myArray[3] = "Hello";
 
-// Add and remove element from front or back end of an array
-myArray.unshift(3); // Add as the first element
-someVar = myArray.shift(); // Remove first element and return it
-myArray.push(3); // Add as the last element
-someVar = myArray.pop(); // Remove last element and return it
+// Add and remove element from front or back end of an array
+myArray.unshift(3); // Add as the first element
+someVar = myArray.shift(); // Remove first element and return it
+myArray.push(3); // Add as the last element
+someVar = myArray.pop(); // Remove last element and return it
 
-// Join all elements of an array with semicolon
+// Join all elements of an array with semicolon
 var myArray0 = [32,false,"js",12,56,90];
-myArray0.join(";") // = "32;false;js;12;56;90"
+myArray0.join(";"); // = "32;false;js;12;56;90"
 
-// Get subarray of elements from index 1 (include) to 4 (exclude)
-myArray0.slice(1,4); // = [false,"js",12]
+// Get subarray of elements from index 1 (include) to 4 (exclude)
+myArray0.slice(1,4); // = [false,"js",12]
 
-// Remove 4 elements starting from index 2, and insert there strings
-// "hi","wr" and "ld"; return removed subarray
-myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
-// myArray0 === [32,false,"hi","wr","ld"]
+// Remove 4 elements starting from index 2, and insert there strings
+// "hi","wr" and "ld"; return removed subarray
+myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
+// myArray0 === [32,false,"hi","wr","ld"]
 
-// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
-// languages: an unordered collection of key-value pairs.
+// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
+// languages: an unordered collection of key-value pairs.
 var myObj = {key1: "Hello", key2: "World"};
 
-// Keys are strings, but quotes aren't required if they're a valid
-// JavaScript identifier. Values can be any type.
+// Keys are strings, but quotes aren't required if they're a valid
+// JavaScript identifier. Values can be any type.
 var myObj = {myKey: "myValue", "my other key": 4};
 
-// Object attributes can also be accessed using the subscript syntax,
-myObj["my other key"]; // = 4
+// Object attributes can also be accessed using the subscript syntax,
+myObj["my other key"]; // = 4
 
-// ... or using the dot syntax, provided the key is a valid identifier.
-myObj.myKey; // = "myValue"
+// ... or using the dot syntax, provided the key is a valid identifier.
+myObj.myKey; // = "myValue"
 
-// Objects are mutable; values can be changed and new keys added.
+// Objects are mutable; values can be changed and new keys added.
 myObj.myThirdKey = true;
 
-// If you try to access a value that's not yet set, you'll get undefined.
-myObj.myFourthKey; // = undefined
+// If you try to access a value that's not yet set, you'll get undefined.
+myObj.myFourthKey; // = undefined
 
-///////////////////////////////////
-// 3. Logic and Control Structures
+///////////////////////////////////
+// 3. Logic and Control Structures
 
-// The `if` structure works as you'd expect.
+// The `if` structure works as you'd expect.
 var count = 1;
 if (count == 3){
-    // evaluated if count is 3
+    // evaluated if count is 3
 } else if (count == 4){
-    // evaluated if count is 4
+    // evaluated if count is 4
 } else {
-    // evaluated if it's not either 3 or 4
+    // evaluated if it's not either 3 or 4
 }
 
-// As does `while`.
+// As does `while`.
 while (true){
-    // An infinite loop!
+    // An infinite loop!
 }
 
-// Do-while loops are like while loops, except they always run at least once.
+// Do-while loops are like while loops, except they always run at least once.
 var input;
 do {
     input = getInput();
 } while (!isValid(input));
 
-// The `for` loop is the same as C and Java:
-// initialization; continue condition; iteration.
+// The `for` loop is the same as C and Java:
+// initialization; continue condition; iteration.
 for (var i = 0; i < 5; i++){
-    // will run 5 times
+    // will run 5 times
 }
 
-// Breaking out of labeled loops is similar to Java
+// Breaking out of labeled loops is similar to Java
 outer:
 for (var i = 0; i < 10; i++) {
     for (var j = 0; j < 10; j++) {
         if (i == 5 && j ==5) {
             break outer;
-            // breaks out of outer loop instead of only the inner one
+            // breaks out of outer loop instead of only the inner one
         }
     }
 }
 
-// The for/in statement allows iteration over properties of an object.
+// The for/in statement allows iteration over properties of an object.
 var description = "";
 var person = {fname:"Paul", lname:"Ken", age:18};
 for (var x in person){
     description += person[x] + " ";
-} // description = 'Paul Ken 18 '
+} // description = 'Paul Ken 18 '
 
-// The for/of statement allows iteration over iterable objects (including the built-in String, 
-// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
-// and user-defined iterables).
+// The for/of statement allows iteration over iterable objects (including the built-in String, 
+// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
+// and user-defined iterables).
 var myPets = "";
 var pets = ["cat", "dog", "hamster", "hedgehog"];
 for (var pet of pets){
     myPets += pet + " ";
-} // myPets = 'cat dog hamster hedgehog '
+} // myPets = 'cat dog hamster hedgehog '
 
-// && is logical and, || is logical or
+// && is logical and, || is logical or
 if (house.size == "big" && house.colour == "blue"){
     house.contains = "bear";
 }
 if (colour == "red" || colour == "blue"){
-    // colour is either red or blue
+    // colour is either red or blue
 }
 
-// && and || "short circuit", which is useful for setting default values.
+// && and || "short circuit", which is useful for setting default values.
 var name = otherName || "default";
 
-// The `switch` statement checks for equality with `===`.
-// Use 'break' after each case
-// or the cases after the correct one will be executed too.
+// The `switch` statement checks for equality with `===`.
+// Use 'break' after each case
+// or the cases after the correct one will be executed too.
 grade = 'B';
 switch (grade) {
   case 'A':
@@ -282,172 +282,172 @@
 }
 
 
-///////////////////////////////////
-// 4. Functions, Scope and Closures
+///////////////////////////////////
+// 4. Functions, Scope and Closures
 
-// JavaScript functions are declared with the `function` keyword.
+// JavaScript functions are declared with the `function` keyword.
 function myFunction(thing){
     return thing.toUpperCase();
 }
-myFunction("foo"); // = "FOO"
+myFunction("foo"); // = "FOO"
 
-// Note that the value to be returned must start on the same line as the
-// `return` keyword, otherwise you'll always return `undefined` due to
-// automatic semicolon insertion. Watch out for this when using Allman style.
+// Note that the value to be returned must start on the same line as the
+// `return` keyword, otherwise you'll always return `undefined` due to
+// automatic semicolon insertion. Watch out for this when using Allman style.
 function myFunction(){
-    return // <- semicolon automatically inserted here
+    return // <- semicolon automatically inserted here
     {thisIsAn: 'object literal'};
 }
-myFunction(); // = undefined
+myFunction(); // = undefined
 
-// JavaScript functions are first class objects, so they can be reassigned to
-// different variable names and passed to other functions as arguments - for
-// example, when supplying an event handler:
+// JavaScript functions are first class objects, so they can be reassigned to
+// different variable names and passed to other functions as arguments - for
+// example, when supplying an event handler:
 function myFunction(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }
 setTimeout(myFunction, 5000);
-// Note: setTimeout isn't part of the JS language, but is provided by browsers
-// and Node.js.
+// Note: setTimeout isn't part of the JS language, but is provided by browsers
+// and Node.js.
 
-// Another function provided by browsers is setInterval
+// Another function provided by browsers is setInterval
 function myFunction(){
-    // this code will be called every 5 seconds
+    // this code will be called every 5 seconds
 }
 setInterval(myFunction, 5000);
 
-// Function objects don't even have to be declared with a name - you can write
-// an anonymous function definition directly into the arguments of another.
+// Function objects don't even have to be declared with a name - you can write
+// an anonymous function definition directly into the arguments of another.
 setTimeout(function(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }, 5000);
 
-// JavaScript has function scope; functions get their own scope but other blocks
-// do not.
+// JavaScript has function scope; functions get their own scope but other blocks
+// do not.
 if (true){
     var i = 5;
 }
-i; // = 5 - not undefined as you'd expect in a block-scoped language
+i; // = 5 - not undefined as you'd expect in a block-scoped language
 
-// This has led to a common pattern of "immediately-executing anonymous
-// functions", which prevent temporary variables from leaking into the global
-// scope.
+// This has led to a common pattern of "immediately-executing anonymous
+// functions", which prevent temporary variables from leaking into the global
+// scope.
 (function(){
     var temporary = 5;
-    // We can access the global scope by assigning to the "global object", which
-    // in a web browser is always `window`. The global object may have a
-    // different name in non-browser environments such as Node.js.
+    // We can access the global scope by assigning to the "global object", which
+    // in a web browser is always `window`. The global object may have a
+    // different name in non-browser environments such as Node.js.
     window.permanent = 10;
 })();
-temporary; // raises ReferenceError
-permanent; // = 10
+temporary; // raises ReferenceError
+permanent; // = 10
 
-// One of JavaScript's most powerful features is closures. If a function is
-// defined inside another function, the inner function has access to all the
-// outer function's variables, even after the outer function exits.
+// One of JavaScript's most powerful features is closures. If a function is
+// defined inside another function, the inner function has access to all the
+// outer function's variables, even after the outer function exits.
 function sayHelloInFiveSeconds(name){
     var prompt = "Hello, " + name + "!";
-    // Inner functions are put in the local scope by default, as if they were
-    // declared with `var`.
+    // Inner functions are put in the local scope by default, as if they were
+    // declared with `var`.
     function inner(){
         alert(prompt);
     }
     setTimeout(inner, 5000);
-    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
-    // exit immediately, and setTimeout will call inner afterwards. However,
-    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
-    // access to the `prompt` variable when it is finally called.
+    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
+    // exit immediately, and setTimeout will call inner afterwards. However,
+    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
+    // access to the `prompt` variable when it is finally called.
 }
-sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
+sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
 
-///////////////////////////////////
-// 5. More about Objects; Constructors and Prototypes
+///////////////////////////////////
+// 5. More about Objects; Constructors and Prototypes
 
-// Objects can contain functions.
+// Objects can contain functions.
 var myObj = {
     myFunc: function(){
         return "Hello world!";
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// When functions attached to an object are called, they can access the object
-// they're attached to using the `this` keyword.
+// When functions attached to an object are called, they can access the object
+// they're attached to using the `this` keyword.
 myObj = {
     myString: "Hello world!",
     myFunc: function(){
         return this.myString;
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// What this is set to has to do with how the function is called, not where
-// it's defined. So, our function doesn't work if it isn't called in the
-// context of the object.
+// What this is set to has to do with how the function is called, not where
+// it's defined. So, our function doesn't work if it isn't called in the
+// context of the object.
 var myFunc = myObj.myFunc;
-myFunc(); // = undefined
+myFunc(); // = undefined
 
-// Inversely, a function can be assigned to the object and gain access to it
-// through `this`, even if it wasn't attached when it was defined.
+// Inversely, a function can be assigned to the object and gain access to it
+// through `this`, even if it wasn't attached when it was defined.
 var myOtherFunc = function(){
     return this.myString.toUpperCase();
 };
 myObj.myOtherFunc = myOtherFunc;
-myObj.myOtherFunc(); // = "HELLO WORLD!"
+myObj.myOtherFunc(); // = "HELLO WORLD!"
 
-// We can also specify a context for a function to execute in when we invoke it
-// using `call` or `apply`.
+// We can also specify a context for a function to execute in when we invoke it
+// using `call` or `apply`.
 
 var anotherFunc = function(s){
     return this.myString + s;
 };
-anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
+anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
 
-// The `apply` function is nearly identical, but takes an array for an argument
-// list.
+// The `apply` function is nearly identical, but takes an array for an argument
+// list.
 
-anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
+anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
 
-// This is useful when working with a function that accepts a sequence of
-// arguments and you want to pass an array.
+// This is useful when working with a function that accepts a sequence of
+// arguments and you want to pass an array.
 
-Math.min(42, 6, 27); // = 6
-Math.min([42, 6, 27]); // = NaN (uh-oh!)
-Math.min.apply(Math, [42, 6, 27]); // = 6
+Math.min(42, 6, 27); // = 6
+Math.min([42, 6, 27]); // = NaN (uh-oh!)
+Math.min.apply(Math, [42, 6, 27]); // = 6
 
-// But, `call` and `apply` are only temporary. When we want it to stick, we can
-// use `bind`.
+// But, `call` and `apply` are only temporary. When we want it to stick, we can
+// use `bind`.
 
 var boundFunc = anotherFunc.bind(myObj);
-boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
+boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
 
-// `bind` can also be used to partially apply (curry) a function.
+// `bind` can also be used to partially apply (curry) a function.
 
 var product = function(a, b){ return a * b; };
 var doubler = product.bind(this, 2);
-doubler(8); // = 16
+doubler(8); // = 16
 
-// When you call a function with the `new` keyword, a new object is created, and
-// made available to the function via the `this` keyword. Functions designed to be
-// called like that are called constructors.
+// When you call a function with the `new` keyword, a new object is created, and
+// made available to the function via the `this` keyword. Functions designed to be
+// called like that are called constructors.
 
 var MyConstructor = function(){
     this.myNumber = 5;
 };
-myNewObj = new MyConstructor(); // = {myNumber: 5}
-myNewObj.myNumber; // = 5
+myNewObj = new MyConstructor(); // = {myNumber: 5}
+myNewObj.myNumber; // = 5
 
-// Unlike most other popular object-oriented languages, JavaScript has no
-// concept of 'instances' created from 'class' blueprints; instead, JavaScript
-// combines instantiation and inheritance into a single concept: a 'prototype'.
+// Unlike most other popular object-oriented languages, JavaScript has no
+// concept of 'instances' created from 'class' blueprints; instead, JavaScript
+// combines instantiation and inheritance into a single concept: a 'prototype'.
 
-// Every JavaScript object has a 'prototype'. When you go to access a property
-// on an object that doesn't exist on the actual object, the interpreter will
-// look at its prototype.
+// Every JavaScript object has a 'prototype'. When you go to access a property
+// on an object that doesn't exist on the actual object, the interpreter will
+// look at its prototype.
 
-// Some JS implementations let you access an object's prototype on the magic
-// property `__proto__`. While this is useful for explaining prototypes it's not
-// part of the standard; we'll get to standard ways of using prototypes later.
+// Some JS implementations let you access an object's prototype on the magic
+// property `__proto__`. While this is useful for explaining prototypes it's not
+// part of the standard; we'll get to standard ways of using prototypes later.
 var myObj = {
     myString: "Hello world!"
 };
@@ -459,58 +459,58 @@
 };
 
 myObj.__proto__ = myPrototype;
-myObj.meaningOfLife; // = 42
+myObj.meaningOfLife; // = 42
 
-// This works for functions, too.
-myObj.myFunc(); // = "hello world!"
+// This works for functions, too.
+myObj.myFunc(); // = "hello world!"
 
-// Of course, if your property isn't on your prototype, the prototype's
-// prototype is searched, and so on.
+// Of course, if your property isn't on your prototype, the prototype's
+// prototype is searched, and so on.
 myPrototype.__proto__ = {
     myBoolean: true
 };
-myObj.myBoolean; // = true
+myObj.myBoolean; // = true
 
-// There's no copying involved here; each object stores a reference to its
-// prototype. This means we can alter the prototype and our changes will be
-// reflected everywhere.
+// There's no copying involved here; each object stores a reference to its
+// prototype. This means we can alter the prototype and our changes will be
+// reflected everywhere.
 myPrototype.meaningOfLife = 43;
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The for/in statement allows iteration over properties of an object,
-// walking up the prototype chain until it sees a null prototype.
+// The for/in statement allows iteration over properties of an object,
+// walking up the prototype chain until it sees a null prototype.
 for (var x in myObj){
     console.log(myObj[x]);
 }
-///prints:
-// Hello world!
-// 43
-// [Function: myFunc]
-// true
+///prints:
+// Hello world!
+// 43
+// [Function: myFunc]
+// true
 
-// To only consider properties attached to the object itself
-// and not its prototypes, use the `hasOwnProperty()` check.
+// To only consider properties attached to the object itself
+// and not its prototypes, use the `hasOwnProperty()` check.
 for (var x in myObj){
     if (myObj.hasOwnProperty(x)){
         console.log(myObj[x]);
     }
 }
-///prints:
-// Hello world!
+///prints:
+// Hello world!
 
-// We mentioned that `__proto__` was non-standard, and there's no standard way to
-// change the prototype of an existing object. However, there are two ways to
-// create a new object with a given prototype.
+// We mentioned that `__proto__` was non-standard, and there's no standard way to
+// change the prototype of an existing object. However, there are two ways to
+// create a new object with a given prototype.
 
-// The first is Object.create, which is a recent addition to JS, and therefore
-// not available in all implementations yet.
+// The first is Object.create, which is a recent addition to JS, and therefore
+// not available in all implementations yet.
 var myObj = Object.create(myPrototype);
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The second way, which works anywhere, has to do with constructors.
-// Constructors have a property called prototype. This is *not* the prototype of
-// the constructor function itself; instead, it's the prototype that new objects
-// are given when they're created with that constructor and the new keyword.
+// The second way, which works anywhere, has to do with constructors.
+// Constructors have a property called prototype. This is *not* the prototype of
+// the constructor function itself; instead, it's the prototype that new objects
+// are given when they're created with that constructor and the new keyword.
 MyConstructor.prototype = {
     myNumber: 5,
     getMyNumber: function(){
@@ -518,47 +518,89 @@
     }
 };
 var myNewObj2 = new MyConstructor();
-myNewObj2.getMyNumber(); // = 5
+myNewObj2.getMyNumber(); // = 5
 myNewObj2.myNumber = 6;
-myNewObj2.getMyNumber(); // = 6
+myNewObj2.getMyNumber(); // = 6
 
-// Built-in types like strings and numbers also have constructors that create
-// equivalent wrapper objects.
+// Built-in types like strings and numbers also have constructors that create
+// equivalent wrapper objects.
 var myNumber = 12;
 var myNumberObj = new Number(12);
-myNumber == myNumberObj; // = true
+myNumber == myNumberObj; // = true
 
-// Except, they aren't exactly equivalent.
-typeof myNumber; // = 'number'
-typeof myNumberObj; // = 'object'
-myNumber === myNumberObj; // = false
+// Except, they aren't exactly equivalent.
+typeof myNumber; // = 'number'
+typeof myNumberObj; // = 'object'
+myNumber === myNumberObj; // = false
 if (0){
-    // This code won't execute, because 0 is falsy.
+    // This code won't execute, because 0 is falsy.
 }
 if (new Number(0)){
-   // This code will execute, because wrapped numbers are objects, and objects
-   // are always truthy.
+   // This code will execute, because wrapped numbers are objects, and objects
+   // are always truthy.
 }
 
-// However, the wrapper objects and the regular builtins share a prototype, so
-// you can actually add functionality to a string, for instance.
+// However, the wrapper objects and the regular builtins share a prototype, so
+// you can actually add functionality to a string, for instance.
 String.prototype.firstCharacter = function(){
     return this.charAt(0);
 };
-"abc".firstCharacter(); // = "a"
+"abc".firstCharacter(); // = "a"
 
-// This fact is often used in "polyfilling", which is implementing newer
-// features of JavaScript in an older subset of JavaScript, so that they can be
-// used in older environments such as outdated browsers.
+// This fact is often used in "polyfilling", which is implementing newer
+// features of JavaScript in an older subset of JavaScript, so that they can be
+// used in older environments such as outdated browsers.
 
-// For instance, we mentioned that Object.create isn't yet available in all
-// implementations, but we can still use it with this polyfill:
-if (Object.create === undefined){ // don't overwrite it if it exists
+// For instance, we mentioned that Object.create isn't yet available in all
+// implementations, but we can still use it with this polyfill:
+if (Object.create === undefined){ // don't overwrite it if it exists
     Object.create = function(proto){
-        // make a temporary constructor with the right prototype
+        // make a temporary constructor with the right prototype
         var Constructor = function(){};
         Constructor.prototype = proto;
-        // then use it to create a new, appropriately-prototyped object
+        // then use it to create a new, appropriately-prototyped object
         return new Constructor();
     };
 }
+
+// ES6 Additions
+
+// The "let" keyword allows you to define variables in a lexical scope, 
+// as opposed to a block scope like the var keyword does.
+let name = "Billy";
+
+// Variables defined with let can be reassigned new values.
+name = "William";
+
+// The "const" keyword allows you to define a variable in a lexical scope
+// like with let, but you cannot reassign the value once one has been assigned.
+
+const pi = 3.14;
+
+pi = 4.13; // You cannot do this.
+
+// There is a new syntax for functions in ES6 known as "lambda syntax".
+// This allows functions to be defined in a lexical scope like with variables
+// defined by const and let. 
+
+const isEven = (number) => {
+    return number % 2 === 0;
+};
+
+isEven(7); // false
+
+// The "equivalent" of this function in the traditional syntax would look like this:
+
+function isEven(number) {
+    return number % 2 === 0;
+};
+
+// I put the word "equivalent" in double quotes because a function defined
+// using the lambda syntax cannnot be called before the definition.
+// The following is an example of invalid usage:
+
+add(1, 8);
+
+const add = (firstNumber, secondNumber) => {
+    return firstNumber + secondNumber;
+};
diff --git a/tests/results/22 b/tests/results/22
index 47840a1..bfd13d3 100644
--- a/tests/results/22
+++ b/tests/results/22
@@ -1,270 +1,270 @@
-// Single-line comments start with two slashes.
-/* Multiline comments start with slash-star,
-   and end with star-slash */
+// Single-line comments start with two slashes.
+/* Multiline comments start with slash-star,
+   and end with star-slash */
 
-// Statements can be terminated by ;
+// Statements can be terminated by ;
 doStuff();
 
-// ... but they don't have to be, as semicolons are automatically inserted
-// wherever there's a newline, except in certain cases.
+// ... but they don't have to be, as semicolons are automatically inserted
+// wherever there's a newline, except in certain cases.
 doStuff()
 
-// Because those cases can cause unexpected results, we'll keep on using
-// semicolons in this guide.
+// Because those cases can cause unexpected results, we'll keep on using
+// semicolons in this guide.
 
-///////////////////////////////////
-// 1. Numbers, Strings and Operators
+///////////////////////////////////
+// 1. Numbers, Strings and Operators
 
-// JavaScript has one number type (which is a 64-bit IEEE 754 double).
-// Doubles have a 52-bit mantissa, which is enough to store integers
-// up to about 9✕10¹⁵ precisely.
-3; // = 3
-1.5; // = 1.5
+// JavaScript has one number type (which is a 64-bit IEEE 754 double).
+// Doubles have a 52-bit mantissa, which is enough to store integers
+// up to about 9✕10¹⁵ precisely.
+3; // = 3
+1.5; // = 1.5
 
-// Some basic arithmetic works as you'd expect.
-1 + 1; // = 2
-0.1 + 0.2; // = 0.30000000000000004
-8 - 1; // = 7
-10 * 2; // = 20
-35 / 5; // = 7
+// Some basic arithmetic works as you'd expect.
+1 + 1; // = 2
+0.1 + 0.2; // = 0.30000000000000004
+8 - 1; // = 7
+10 * 2; // = 20
+35 / 5; // = 7
 
-// Including uneven division.
-5 / 2; // = 2.5
+// Including uneven division.
+5 / 2; // = 2.5
 
-// And modulo division.
-10 % 2; // = 0
-30 % 4; // = 2
-18.5 % 7; // = 4.5
+// And modulo division.
+10 % 2; // = 0
+30 % 4; // = 2
+18.5 % 7; // = 4.5
 
-// Bitwise operations also work; when you perform a bitwise operation your float
-// is converted to a signed int *up to* 32 bits.
-1 << 2; // = 4
+// Bitwise operations also work; when you perform a bitwise operation your float
+// is converted to a signed int *up to* 32 bits.
+1 << 2; // = 4
 
-// Precedence is enforced with parentheses.
-(1 + 3) * 2; // = 8
+// Precedence is enforced with parentheses.
+(1 + 3) * 2; // = 8
 
-// There are three special not-a-real-number values:
-Infinity; // result of e.g. 1/0
--Infinity; // result of e.g. -1/0
-NaN; // result of e.g. 0/0, stands for 'Not a Number'
+// There are three special not-a-real-number values:
+Infinity; // result of e.g. 1/0
+-Infinity; // result of e.g. -1/0
+NaN; // result of e.g. 0/0, stands for 'Not a Number'
 
-// There's also a boolean type.
+// There's also a boolean type.
 true;
 false;
 
-// Strings are created with ' or ".
+// Strings are created with ' or ".
 'abc';
 "Hello, world";
 
-// Negation uses the ! symbol
-!true; // = false
-!false; // = true
+// Negation uses the ! symbol
+!true; // = false
+!false; // = true
 
-// Equality is ===
-1 === 1; // = true
-2 === 1; // = false
+// Equality is ===
+1 === 1; // = true
+2 === 1; // = false
 
-// Inequality is !==
-1 !== 1; // = false
-2 !== 1; // = true
+// Inequality is !==
+1 !== 1; // = false
+2 !== 1; // = true
 
-// More comparisons
-1 < 10; // = true
-1 > 10; // = false
-2 <= 2; // = true
-2 >= 2; // = true
+// More comparisons
+1 < 10; // = true
+1 > 10; // = false
+2 <= 2; // = true
+2 >= 2; // = true
 
-// Strings are concatenated with +
-"Hello " + "world!"; // = "Hello world!"
+// Strings are concatenated with +
+"Hello " + "world!"; // = "Hello world!"
 
-// ... which works with more than just strings
-"1, 2, " + 3; // = "1, 2, 3"
-"Hello " + ["world", "!"]; // = "Hello world,!"
+// ... which works with more than just strings
+"1, 2, " + 3; // = "1, 2, 3"
+"Hello " + ["world", "!"]; // = "Hello world,!"
 
-// and are compared with < and >
-"a" < "b"; // = true
+// and are compared with < and >
+"a" < "b"; // = true
 
-// Type coercion is performed for comparisons with double equals...
-"5" == 5; // = true
-null == undefined; // = true
+// Type coercion is performed for comparisons with double equals...
+"5" == 5; // = true
+null == undefined; // = true
 
-// ...unless you use ===
-"5" === 5; // = false
-null === undefined; // = false
+// ...unless you use ===
+"5" === 5; // = false
+null === undefined; // = false
 
-// ...which can result in some weird behaviour...
-13 + !0; // 14
-"13" + !0; // '13true'
+// ...which can result in some weird behaviour...
+13 + !0; // 14
+"13" + !0; // '13true'
 
-// You can access characters in a string with `charAt`
-"This is a string".charAt(0);  // = 'T'
+// You can access characters in a string with `charAt`
+"This is a string".charAt(0);  // = 'T'
 
-// ...or use `substring` to get larger pieces.
-"Hello world".substring(0, 5); // = "Hello"
+// ...or use `substring` to get larger pieces.
+"Hello world".substring(0, 5); // = "Hello"
 
-// `length` is a property, so don't use ().
-"Hello".length; // = 5
+// `length` is a property, so don't use ().
+"Hello".length; // = 5
 
-// There's also `null` and `undefined`.
-null;      // used to indicate a deliberate non-value
-undefined; // used to indicate a value is not currently present (although
-           // `undefined` is actually a value itself)
+// There's also `null` and `undefined`.
+null;      // used to indicate a deliberate non-value
+undefined; // used to indicate a value is not currently present (although
+           // `undefined` is actually a value itself)
 
-// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
-// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
+// false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy.
+// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
 
-///////////////////////////////////
-// 2. Variables, Arrays and Objects
+///////////////////////////////////
+// 2. Variables, Arrays and Objects
 
-// Variables are declared with the `var` keyword. JavaScript is dynamically
-// typed, so you don't need to specify type. Assignment uses a single `=`
-// character.
+// Variables are declared with the `var` keyword. JavaScript is dynamically
+// typed, so you don't need to specify type. Assignment uses a single `=`
+// character.
 var someVar = 5;
 
-// If you leave the var keyword off, you won't get an error...
+// If you leave the var keyword off, you won't get an error...
 someOtherVar = 10;
 
-// ...but your variable will be created in the global scope, not in the scope
-// you defined it in.
+// ...but your variable will be created in the global scope, not in the scope
+// you defined it in.
 
-// Variables declared without being assigned to are set to undefined.
-var someThirdVar; // = undefined
+// Variables declared without being assigned to are set to undefined.
+var someThirdVar; // = undefined
 
-// If you want to declare a couple of variables, then you could use a comma
-// separator
+// If you want to declare a couple of variables, then you could use a comma
+// separator
 var someFourthVar = 2, someFifthVar = 4;
 
-// There's shorthand for performing math operations on variables:
-someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
-someVar *= 10; // now someVar is 100
+// There's shorthand for performing math operations on variables:
+someVar += 5; // equivalent to someVar = someVar + 5; someVar is 10 now
+someVar *= 10; // now someVar is 100
 
-// and an even-shorter-hand for adding or subtracting 1
-someVar++; // now someVar is 101
-someVar--; // back to 100
+// and an even-shorter-hand for adding or subtracting 1
+someVar++; // now someVar is 101
+someVar--; // back to 100
 
-// Arrays are ordered lists of values, of any type.
+// Arrays are ordered lists of values, of any type.
 var myArray = ["Hello", 45, true];
 
-// Their members can be accessed using the square-brackets subscript syntax.
-// Array indices start at zero.
-myArray[1]; // = 45
+// Their members can be accessed using the square-brackets subscript syntax.
+// Array indices start at zero.
+myArray[1]; // = 45
 
-// Arrays are mutable and of variable length.
+// Arrays are mutable and of variable length.
 myArray.push("World");
-myArray.length; // = 4
+myArray.length; // = 4
 
-// Add/Modify at specific index
+// Add/Modify at specific index
 myArray[3] = "Hello";
 
-// Add and remove element from front or back end of an array
-myArray.unshift(3); // Add as the first element
-someVar = myArray.shift(); // Remove first element and return it
-myArray.push(3); // Add as the last element
-someVar = myArray.pop(); // Remove last element and return it
+// Add and remove element from front or back end of an array
+myArray.unshift(3); // Add as the first element
+someVar = myArray.shift(); // Remove first element and return it
+myArray.push(3); // Add as the last element
+someVar = myArray.pop(); // Remove last element and return it
 
-// Join all elements of an array with semicolon
+// Join all elements of an array with semicolon
 var myArray0 = [32,false,"js",12,56,90];
-myArray0.join(";") // = "32;false;js;12;56;90"
+myArray0.join(";"); // = "32;false;js;12;56;90"
 
-// Get subarray of elements from index 1 (include) to 4 (exclude)
-myArray0.slice(1,4); // = [false,"js",12]
+// Get subarray of elements from index 1 (include) to 4 (exclude)
+myArray0.slice(1,4); // = [false,"js",12]
 
-// Remove 4 elements starting from index 2, and insert there strings
-// "hi","wr" and "ld"; return removed subarray
-myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
-// myArray0 === [32,false,"hi","wr","ld"]
+// Remove 4 elements starting from index 2, and insert there strings
+// "hi","wr" and "ld"; return removed subarray
+myArray0.splice(2,4,"hi","wr","ld"); // = ["js",12,56,90]
+// myArray0 === [32,false,"hi","wr","ld"]
 
-// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
-// languages: an unordered collection of key-value pairs.
+// JavaScript's objects are equivalent to "dictionaries" or "maps" in other
+// languages: an unordered collection of key-value pairs.
 var myObj = {key1: "Hello", key2: "World"};
 
-// Keys are strings, but quotes aren't required if they're a valid
-// JavaScript identifier. Values can be any type.
+// Keys are strings, but quotes aren't required if they're a valid
+// JavaScript identifier. Values can be any type.
 var myObj = {myKey: "myValue", "my other key": 4};
 
-// Object attributes can also be accessed using the subscript syntax,
-myObj["my other key"]; // = 4
+// Object attributes can also be accessed using the subscript syntax,
+myObj["my other key"]; // = 4
 
-// ... or using the dot syntax, provided the key is a valid identifier.
-myObj.myKey; // = "myValue"
+// ... or using the dot syntax, provided the key is a valid identifier.
+myObj.myKey; // = "myValue"
 
-// Objects are mutable; values can be changed and new keys added.
+// Objects are mutable; values can be changed and new keys added.
 myObj.myThirdKey = true;
 
-// If you try to access a value that's not yet set, you'll get undefined.
-myObj.myFourthKey; // = undefined
+// If you try to access a value that's not yet set, you'll get undefined.
+myObj.myFourthKey; // = undefined
 
-///////////////////////////////////
-// 3. Logic and Control Structures
+///////////////////////////////////
+// 3. Logic and Control Structures
 
-// The `if` structure works as you'd expect.
+// The `if` structure works as you'd expect.
 var count = 1;
 if (count == 3){
-    // evaluated if count is 3
+    // evaluated if count is 3
 } else if (count == 4){
-    // evaluated if count is 4
+    // evaluated if count is 4
 } else {
-    // evaluated if it's not either 3 or 4
+    // evaluated if it's not either 3 or 4
 }
 
-// As does `while`.
+// As does `while`.
 while (true){
-    // An infinite loop!
+    // An infinite loop!
 }
 
-// Do-while loops are like while loops, except they always run at least once.
+// Do-while loops are like while loops, except they always run at least once.
 var input;
 do {
     input = getInput();
 } while (!isValid(input));
 
-// The `for` loop is the same as C and Java:
-// initialization; continue condition; iteration.
+// The `for` loop is the same as C and Java:
+// initialization; continue condition; iteration.
 for (var i = 0; i < 5; i++){
-    // will run 5 times
+    // will run 5 times
 }
 
-// Breaking out of labeled loops is similar to Java
+// Breaking out of labeled loops is similar to Java
 outer:
 for (var i = 0; i < 10; i++) {
     for (var j = 0; j < 10; j++) {
         if (i == 5 && j ==5) {
             break outer;
-            // breaks out of outer loop instead of only the inner one
+            // breaks out of outer loop instead of only the inner one
         }
     }
 }
 
-// The for/in statement allows iteration over properties of an object.
+// The for/in statement allows iteration over properties of an object.
 var description = "";
 var person = {fname:"Paul", lname:"Ken", age:18};
 for (var x in person){
     description += person[x] + " ";
-} // description = 'Paul Ken 18 '
+} // description = 'Paul Ken 18 '
 
-// The for/of statement allows iteration over iterable objects (including the built-in String, 
-// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
-// and user-defined iterables).
+// The for/of statement allows iteration over iterable objects (including the built-in String, 
+// Array, e.g. the Array-like arguments or NodeList objects, TypedArray, Map and Set, 
+// and user-defined iterables).
 var myPets = "";
 var pets = ["cat", "dog", "hamster", "hedgehog"];
 for (var pet of pets){
     myPets += pet + " ";
-} // myPets = 'cat dog hamster hedgehog '
+} // myPets = 'cat dog hamster hedgehog '
 
-// && is logical and, || is logical or
+// && is logical and, || is logical or
 if (house.size == "big" && house.colour == "blue"){
     house.contains = "bear";
 }
 if (colour == "red" || colour == "blue"){
-    // colour is either red or blue
+    // colour is either red or blue
 }
 
-// && and || "short circuit", which is useful for setting default values.
+// && and || "short circuit", which is useful for setting default values.
 var name = otherName || "default";
 
-// The `switch` statement checks for equality with `===`.
-// Use 'break' after each case
-// or the cases after the correct one will be executed too.
+// The `switch` statement checks for equality with `===`.
+// Use 'break' after each case
+// or the cases after the correct one will be executed too.
 grade = 'B';
 switch (grade) {
   case 'A':
@@ -282,172 +282,172 @@
 }
 
 
-///////////////////////////////////
-// 4. Functions, Scope and Closures
+///////////////////////////////////
+// 4. Functions, Scope and Closures
 
-// JavaScript functions are declared with the `function` keyword.
+// JavaScript functions are declared with the `function` keyword.
 function myFunction(thing){
     return thing.toUpperCase();
 }
-myFunction("foo"); // = "FOO"
+myFunction("foo"); // = "FOO"
 
-// Note that the value to be returned must start on the same line as the
-// `return` keyword, otherwise you'll always return `undefined` due to
-// automatic semicolon insertion. Watch out for this when using Allman style.
+// Note that the value to be returned must start on the same line as the
+// `return` keyword, otherwise you'll always return `undefined` due to
+// automatic semicolon insertion. Watch out for this when using Allman style.
 function myFunction(){
-    return // <- semicolon automatically inserted here
+    return // <- semicolon automatically inserted here
     {thisIsAn: 'object literal'};
 }
-myFunction(); // = undefined
+myFunction(); // = undefined
 
-// JavaScript functions are first class objects, so they can be reassigned to
-// different variable names and passed to other functions as arguments - for
-// example, when supplying an event handler:
+// JavaScript functions are first class objects, so they can be reassigned to
+// different variable names and passed to other functions as arguments - for
+// example, when supplying an event handler:
 function myFunction(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }
 setTimeout(myFunction, 5000);
-// Note: setTimeout isn't part of the JS language, but is provided by browsers
-// and Node.js.
+// Note: setTimeout isn't part of the JS language, but is provided by browsers
+// and Node.js.
 
-// Another function provided by browsers is setInterval
+// Another function provided by browsers is setInterval
 function myFunction(){
-    // this code will be called every 5 seconds
+    // this code will be called every 5 seconds
 }
 setInterval(myFunction, 5000);
 
-// Function objects don't even have to be declared with a name - you can write
-// an anonymous function definition directly into the arguments of another.
+// Function objects don't even have to be declared with a name - you can write
+// an anonymous function definition directly into the arguments of another.
 setTimeout(function(){
-    // this code will be called in 5 seconds' time
+    // this code will be called in 5 seconds' time
 }, 5000);
 
-// JavaScript has function scope; functions get their own scope but other blocks
-// do not.
+// JavaScript has function scope; functions get their own scope but other blocks
+// do not.
 if (true){
     var i = 5;
 }
-i; // = 5 - not undefined as you'd expect in a block-scoped language
+i; // = 5 - not undefined as you'd expect in a block-scoped language
 
-// This has led to a common pattern of "immediately-executing anonymous
-// functions", which prevent temporary variables from leaking into the global
-// scope.
+// This has led to a common pattern of "immediately-executing anonymous
+// functions", which prevent temporary variables from leaking into the global
+// scope.
 (function(){
     var temporary = 5;
-    // We can access the global scope by assigning to the "global object", which
-    // in a web browser is always `window`. The global object may have a
-    // different name in non-browser environments such as Node.js.
+    // We can access the global scope by assigning to the "global object", which
+    // in a web browser is always `window`. The global object may have a
+    // different name in non-browser environments such as Node.js.
     window.permanent = 10;
 })();
-temporary; // raises ReferenceError
-permanent; // = 10
+temporary; // raises ReferenceError
+permanent; // = 10
 
-// One of JavaScript's most powerful features is closures. If a function is
-// defined inside another function, the inner function has access to all the
-// outer function's variables, even after the outer function exits.
+// One of JavaScript's most powerful features is closures. If a function is
+// defined inside another function, the inner function has access to all the
+// outer function's variables, even after the outer function exits.
 function sayHelloInFiveSeconds(name){
     var prompt = "Hello, " + name + "!";
-    // Inner functions are put in the local scope by default, as if they were
-    // declared with `var`.
+    // Inner functions are put in the local scope by default, as if they were
+    // declared with `var`.
     function inner(){
         alert(prompt);
     }
     setTimeout(inner, 5000);
-    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
-    // exit immediately, and setTimeout will call inner afterwards. However,
-    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
-    // access to the `prompt` variable when it is finally called.
+    // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will
+    // exit immediately, and setTimeout will call inner afterwards. However,
+    // because inner is "closed over" sayHelloInFiveSeconds, inner still has
+    // access to the `prompt` variable when it is finally called.
 }
-sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
+sayHelloInFiveSeconds("Adam"); // will open a popup with "Hello, Adam!" in 5s
 
-///////////////////////////////////
-// 5. More about Objects; Constructors and Prototypes
+///////////////////////////////////
+// 5. More about Objects; Constructors and Prototypes
 
-// Objects can contain functions.
+// Objects can contain functions.
 var myObj = {
     myFunc: function(){
         return "Hello world!";
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// When functions attached to an object are called, they can access the object
-// they're attached to using the `this` keyword.
+// When functions attached to an object are called, they can access the object
+// they're attached to using the `this` keyword.
 myObj = {
     myString: "Hello world!",
     myFunc: function(){
         return this.myString;
     }
 };
-myObj.myFunc(); // = "Hello world!"
+myObj.myFunc(); // = "Hello world!"
 
-// What this is set to has to do with how the function is called, not where
-// it's defined. So, our function doesn't work if it isn't called in the
-// context of the object.
+// What this is set to has to do with how the function is called, not where
+// it's defined. So, our function doesn't work if it isn't called in the
+// context of the object.
 var myFunc = myObj.myFunc;
-myFunc(); // = undefined
+myFunc(); // = undefined
 
-// Inversely, a function can be assigned to the object and gain access to it
-// through `this`, even if it wasn't attached when it was defined.
+// Inversely, a function can be assigned to the object and gain access to it
+// through `this`, even if it wasn't attached when it was defined.
 var myOtherFunc = function(){
     return this.myString.toUpperCase();
 };
 myObj.myOtherFunc = myOtherFunc;
-myObj.myOtherFunc(); // = "HELLO WORLD!"
+myObj.myOtherFunc(); // = "HELLO WORLD!"
 
-// We can also specify a context for a function to execute in when we invoke it
-// using `call` or `apply`.
+// We can also specify a context for a function to execute in when we invoke it
+// using `call` or `apply`.
 
 var anotherFunc = function(s){
     return this.myString + s;
 };
-anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
+anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!"
 
-// The `apply` function is nearly identical, but takes an array for an argument
-// list.
+// The `apply` function is nearly identical, but takes an array for an argument
+// list.
 
-anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
+anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!"
 
-// This is useful when working with a function that accepts a sequence of
-// arguments and you want to pass an array.
+// This is useful when working with a function that accepts a sequence of
+// arguments and you want to pass an array.
 
-Math.min(42, 6, 27); // = 6
-Math.min([42, 6, 27]); // = NaN (uh-oh!)
-Math.min.apply(Math, [42, 6, 27]); // = 6
+Math.min(42, 6, 27); // = 6
+Math.min([42, 6, 27]); // = NaN (uh-oh!)
+Math.min.apply(Math, [42, 6, 27]); // = 6
 
-// But, `call` and `apply` are only temporary. When we want it to stick, we can
-// use `bind`.
+// But, `call` and `apply` are only temporary. When we want it to stick, we can
+// use `bind`.
 
 var boundFunc = anotherFunc.bind(myObj);
-boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
+boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!"
 
-// `bind` can also be used to partially apply (curry) a function.
+// `bind` can also be used to partially apply (curry) a function.
 
 var product = function(a, b){ return a * b; };
 var doubler = product.bind(this, 2);
-doubler(8); // = 16
+doubler(8); // = 16
 
-// When you call a function with the `new` keyword, a new object is created, and
-// made available to the function via the `this` keyword. Functions designed to be
-// called like that are called constructors.
+// When you call a function with the `new` keyword, a new object is created, and
+// made available to the function via the `this` keyword. Functions designed to be
+// called like that are called constructors.
 
 var MyConstructor = function(){
     this.myNumber = 5;
 };
-myNewObj = new MyConstructor(); // = {myNumber: 5}
-myNewObj.myNumber; // = 5
+myNewObj = new MyConstructor(); // = {myNumber: 5}
+myNewObj.myNumber; // = 5
 
-// Unlike most other popular object-oriented languages, JavaScript has no
-// concept of 'instances' created from 'class' blueprints; instead, JavaScript
-// combines instantiation and inheritance into a single concept: a 'prototype'.
+// Unlike most other popular object-oriented languages, JavaScript has no
+// concept of 'instances' created from 'class' blueprints; instead, JavaScript
+// combines instantiation and inheritance into a single concept: a 'prototype'.
 
-// Every JavaScript object has a 'prototype'. When you go to access a property
-// on an object that doesn't exist on the actual object, the interpreter will
-// look at its prototype.
+// Every JavaScript object has a 'prototype'. When you go to access a property
+// on an object that doesn't exist on the actual object, the interpreter will
+// look at its prototype.
 
-// Some JS implementations let you access an object's prototype on the magic
-// property `__proto__`. While this is useful for explaining prototypes it's not
-// part of the standard; we'll get to standard ways of using prototypes later.
+// Some JS implementations let you access an object's prototype on the magic
+// property `__proto__`. While this is useful for explaining prototypes it's not
+// part of the standard; we'll get to standard ways of using prototypes later.
 var myObj = {
     myString: "Hello world!"
 };
@@ -459,58 +459,58 @@
 };
 
 myObj.__proto__ = myPrototype;
-myObj.meaningOfLife; // = 42
+myObj.meaningOfLife; // = 42
 
-// This works for functions, too.
-myObj.myFunc(); // = "hello world!"
+// This works for functions, too.
+myObj.myFunc(); // = "hello world!"
 
-// Of course, if your property isn't on your prototype, the prototype's
-// prototype is searched, and so on.
+// Of course, if your property isn't on your prototype, the prototype's
+// prototype is searched, and so on.
 myPrototype.__proto__ = {
     myBoolean: true
 };
-myObj.myBoolean; // = true
+myObj.myBoolean; // = true
 
-// There's no copying involved here; each object stores a reference to its
-// prototype. This means we can alter the prototype and our changes will be
-// reflected everywhere.
+// There's no copying involved here; each object stores a reference to its
+// prototype. This means we can alter the prototype and our changes will be
+// reflected everywhere.
 myPrototype.meaningOfLife = 43;
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The for/in statement allows iteration over properties of an object,
-// walking up the prototype chain until it sees a null prototype.
+// The for/in statement allows iteration over properties of an object,
+// walking up the prototype chain until it sees a null prototype.
 for (var x in myObj){
     console.log(myObj[x]);
 }
-///prints:
-// Hello world!
-// 43
-// [Function: myFunc]
-// true
+///prints:
+// Hello world!
+// 43
+// [Function: myFunc]
+// true
 
-// To only consider properties attached to the object itself
-// and not its prototypes, use the `hasOwnProperty()` check.
+// To only consider properties attached to the object itself
+// and not its prototypes, use the `hasOwnProperty()` check.
 for (var x in myObj){
     if (myObj.hasOwnProperty(x)){
         console.log(myObj[x]);
     }
 }
-///prints:
-// Hello world!
+///prints:
+// Hello world!
 
-// We mentioned that `__proto__` was non-standard, and there's no standard way to
-// change the prototype of an existing object. However, there are two ways to
-// create a new object with a given prototype.
+// We mentioned that `__proto__` was non-standard, and there's no standard way to
+// change the prototype of an existing object. However, there are two ways to
+// create a new object with a given prototype.
 
-// The first is Object.create, which is a recent addition to JS, and therefore
-// not available in all implementations yet.
+// The first is Object.create, which is a recent addition to JS, and therefore
+// not available in all implementations yet.
 var myObj = Object.create(myPrototype);
-myObj.meaningOfLife; // = 43
+myObj.meaningOfLife; // = 43
 
-// The second way, which works anywhere, has to do with constructors.
-// Constructors have a property called prototype. This is *not* the prototype of
-// the constructor function itself; instead, it's the prototype that new objects
-// are given when they're created with that constructor and the new keyword.
+// The second way, which works anywhere, has to do with constructors.
+// Constructors have a property called prototype. This is *not* the prototype of
+// the constructor function itself; instead, it's the prototype that new objects
+// are given when they're created with that constructor and the new keyword.
 MyConstructor.prototype = {
     myNumber: 5,
     getMyNumber: function(){
@@ -518,47 +518,89 @@
     }
 };
 var myNewObj2 = new MyConstructor();
-myNewObj2.getMyNumber(); // = 5
+myNewObj2.getMyNumber(); // = 5
 myNewObj2.myNumber = 6;
-myNewObj2.getMyNumber(); // = 6
+myNewObj2.getMyNumber(); // = 6
 
-// Built-in types like strings and numbers also have constructors that create
-// equivalent wrapper objects.
+// Built-in types like strings and numbers also have constructors that create
+// equivalent wrapper objects.
 var myNumber = 12;
 var myNumberObj = new Number(12);
-myNumber == myNumberObj; // = true
+myNumber == myNumberObj; // = true
 
-// Except, they aren't exactly equivalent.
-typeof myNumber; // = 'number'
-typeof myNumberObj; // = 'object'
-myNumber === myNumberObj; // = false
+// Except, they aren't exactly equivalent.
+typeof myNumber; // = 'number'
+typeof myNumberObj; // = 'object'
+myNumber === myNumberObj; // = false
 if (0){
-    // This code won't execute, because 0 is falsy.
+    // This code won't execute, because 0 is falsy.
 }
 if (new Number(0)){
-   // This code will execute, because wrapped numbers are objects, and objects
-   // are always truthy.
+   // This code will execute, because wrapped numbers are objects, and objects
+   // are always truthy.
 }
 
-// However, the wrapper objects and the regular builtins share a prototype, so
-// you can actually add functionality to a string, for instance.
+// However, the wrapper objects and the regular builtins share a prototype, so
+// you can actually add functionality to a string, for instance.
 String.prototype.firstCharacter = function(){
     return this.charAt(0);
 };
-"abc".firstCharacter(); // = "a"
+"abc".firstCharacter(); // = "a"
 
-// This fact is often used in "polyfilling", which is implementing newer
-// features of JavaScript in an older subset of JavaScript, so that they can be
-// used in older environments such as outdated browsers.
+// This fact is often used in "polyfilling", which is implementing newer
+// features of JavaScript in an older subset of JavaScript, so that they can be
+// used in older environments such as outdated browsers.
 
-// For instance, we mentioned that Object.create isn't yet available in all
-// implementations, but we can still use it with this polyfill:
-if (Object.create === undefined){ // don't overwrite it if it exists
+// For instance, we mentioned that Object.create isn't yet available in all
+// implementations, but we can still use it with this polyfill:
+if (Object.create === undefined){ // don't overwrite it if it exists
     Object.create = function(proto){
-        // make a temporary constructor with the right prototype
+        // make a temporary constructor with the right prototype
         var Constructor = function(){};
         Constructor.prototype = proto;
-        // then use it to create a new, appropriately-prototyped object
+        // then use it to create a new, appropriately-prototyped object
         return new Constructor();
     };
 }
+
+// ES6 Additions
+
+// The "let" keyword allows you to define variables in a lexical scope, 
+// as opposed to a block scope like the var keyword does.
+let name = "Billy";
+
+// Variables defined with let can be reassigned new values.
+name = "William";
+
+// The "const" keyword allows you to define a variable in a lexical scope
+// like with let, but you cannot reassign the value once one has been assigned.
+
+const pi = 3.14;
+
+pi = 4.13; // You cannot do this.
+
+// There is a new syntax for functions in ES6 known as "lambda syntax".
+// This allows functions to be defined in a lexical scope like with variables
+// defined by const and let. 
+
+const isEven = (number) => {
+    return number % 2 === 0;
+};
+
+isEven(7); // false
+
+// The "equivalent" of this function in the traditional syntax would look like this:
+
+function isEven(number) {
+    return number % 2 === 0;
+};
+
+// I put the word "equivalent" in double quotes because a function defined
+// using the lambda syntax cannnot be called before the definition.
+// The following is an example of invalid usage:
+
+add(1, 8);
+
+const add = (firstNumber, secondNumber) => {
+    return firstNumber + secondNumber;
+};
diff --git a/tests/results/3 b/tests/results/3
index 41a116a..cfff5cc 100644
--- a/tests/results/3
+++ b/tests/results/3
@@ -1,17 +1,17 @@
-# Displays everything in the target directory
-ls path/to/the/target/directory
+# To display everything in <dir>, excluding hidden files:
+ls <dir>
 
-# Displays everything including hidden files
-ls -a
+# To display everything in <dir>, including hidden files:
+ls -a <dir>
 
-# Displays all files, along with the size (with unit suffixes) and timestamp
-ls -lh 
+# To display all files, along with the size (with unit suffixes) and timestamp
+ls -lh <dir>
 
-# Display files, sorted by size
-ls -S
+# To display files, sorted by size:
+ls -S <dir>
 
-# Display directories only
-ls -d */
+# To display directories only:
+ls -d */ <dir>
 
-# Display directories only, include hidden
-ls -d .*/ */
+# To display directories only, include hidden:
+ls -d .*/ */ <dir>
diff --git a/tests/results/4 b/tests/results/4
index 10b9309..73d1846 100644
--- a/tests/results/4
+++ b/tests/results/4
@@ -1,54 +1,54 @@
-# Create a btrfs file system on /dev/sdb, /dev/sdc, and /dev/sdd
+# Create a btrfs file system on /dev/sdb, /dev/sdc, and /dev/sdd
 mkfs.btrfs /dev/sdb /dev/sdc /dev/sdd
 
-# btrfs with just one hard drive, metadata not redundant 
-# (this is danegerous: if your metadata is lost, your data is lost as well)
+# btrfs with just one hard drive, metadata not redundant
+# (this is danegerous: if your metadata is lost, your data is lost as well)
 mkfs.btrfs -m single /dev/sdb
 
-# data to be redundant and metadata to be non-redundant:
+# data to be redundant and metadata to be non-redundant:
 mkfs.btrfs -m raid0 -d raid1 /dev/sdb /dev/sdc /dev/sdd
 
-# both data and metadata to be redundan
+# both data and metadata to be redundan
 mkfs.btrfs -d raid1 /dev/sdb /dev/sdc /dev/sdd
 
-# To get a list of all btrfs file systems
+# To get a list of all btrfs file systems
 btrfs filesystem show
 
-# detailed df for a fileesystem (mounted in /mnt)
+# detailed df for a fileesystem (mounted in /mnt)
 btrfs filesystem df /mnt
 
-# resize btrfs online (-2g decreases, +2g increases)
+# resize btrfs online (-2g decreases, +2g increases)
 btrfs filesystem resize -2g /mnt
 
-# use maximum space
+# use maximum space
 btrfs filesystem resize max /mnt
 
-# add new device to a filesystem
+# add new device to a filesystem
 btrfs device add /dev/sdf /mnt
 
-# remove devices from a filesystem
+# remove devices from a filesystem
 btrfs device delete missing /mnt
 
-# create the subvolume /mnt/sv1 in the /mnt volume
+# create the subvolume /mnt/sv1 in the /mnt volume
 btrfs subvolume create /mnt/sv1
 
-# list subvolumes
+# list subvolumes
 btrfs subvolume list /mnt
 
-# mount subvolume without mounting the main filesystem
+# mount subvolume without mounting the main filesystem
 mount -o subvol=sv1 /dev/sdb /mnt
 
-# delete subvolume
+# delete subvolume
 btrfs subvolume delete /mnt/sv1
 
-# taking snapshot of a subvolume
+# taking snapshot of a subvolume
 btrfs subvolume snapshot /mnt/sv1 /mnt/sv1_snapshot
 
-# taking snapshot of a file (copy file by reference)
+# taking snapshot of a file (copy file by reference)
 cp --reflink /mnt/sv1/test1 /mnt/sv1/test3
 
-# convert ext3/ext4 to btrfs
+# convert ext3/ext4 to btrfs
 btrfs-convert /dev/sdb1
 
-# convert btrfs to ext3/ext4
+# convert btrfs to ext3/ext4
 btrfs-convert -r /dev/sdb1
diff --git a/tests/results/5 b/tests/results/5
index 317da29..5f6c2ee 100644
--- a/tests/results/5
+++ b/tests/results/5
@@ -1,3 +1,3 @@
  btrfs 
-# create the subvolume /mnt/sv1 in the /mnt volume
+# create the subvolume /mnt/sv1 in the /mnt volume
 btrfs subvolume create /mnt/sv1