Section 12: Object-Oriented Programming and Functional Programming

Question 1

Chapter 67:

What is Object-Oriented Programming.

Answer 1

Where the world is looked at as a collection of objects.

Objects are represented as complex data structures consisting of different attributes and methods.

Objects are instances of Classes; Classes define attributes and methods.

Question 2

Chapter 67:
What is an attribute?
What would be an attribute of a car object?

Answer 2

An object-bound variable.

Brand / Colour / Engine Size.

Question 3

Chapter 67:
What is a method?
What would be a method of a car object?

Answer 3

An object-bound function or procedure.

Accelerate / Break.

Question 4

Chapter 67:

What are the 4 main concepts in OOP?

Answer 4

Instantiation,
Encapsulation,
Inheritance,
Polymorphism.

Question 5

Chapter 67:

What is Encapsulation?

Answer 5

Making attributes hidden, and creating messages to access them.

Question 6

Chapter 67:

What are messages in OOP?

Answer 6

Getters and Setters.

Methods that return the value of a private attribute or change the value of a private attribute.

Question 7

Chapter 67:

What is Inheritance?

Answer 7

Where one class copies the attributes and methods of another class into itself. Other methods and attributes can then be added to personalise the subclass.

Question 8

Chapter 67:

What do we call the different types of classes involved in Inheritance?

Answer 8

Super Class - Parent Class

Sub Class - Child Class

Question 9

Chapter 67:

What rule do we use to determine whether Inheritance is appropriate?

Answer 9

The “is an X a Y” / “is a” rule

For Example:
Is a Cat an Animal?
Yes, therefore Cat should be a subclass of Animal.

Question 10

Chapter 68:

What is Association?

Answer 10

Related but independent classes.

“X has a Y” / “has a” rule.

For Example:
A teacher has a student.
A student has a teacher.
They are Associated, but there is no Ownership between them.

Question 11

Chapter 68:

What is Aggregation?

Answer 11

When one class is contained by another (e.g. A player is part of a team), and the object (player) is not destroyed when the container (team) is destroyed. (The player does not cease to exist if the team disbands).

This can be represented with a hollow diamond on a graph. (With the diamond by the container).

Question 12

Chapter 68:

What is Class Composition?

Answer 12

When one class is contained by another (e.g. A room is part of a hotel), and the object (room) is destroyed when the container (hotel) is destroyed. (When a hotel is destroyed, the rooms are as well).

This can be represented with a solid diamond on a graph. (With the diamond by the container).

Question 13

Chapter 68:
Association can be Unidirectional or Bidirectional.
What is the difference? Give examples.

Answer 13

Unidirectional is one-way.
Bidirectional is two-way.

Examples:
Unidirectional: Customer places an Order.
Bidirectional: A is married to B, B is married to A.

Question 14

Chapter 68:

What is Polymorphism?

Answer 14

As an extension of Inheritance, Polymorphism is where methods are changed for a specific subclass.

For example:
With a superclass Animal, you may have a method moveLeft() which decrements the posX attribute for the object by 3 spaces.
If you have subclasses Cat and Mouse, the mouse may not be able to move 3 spaces at once, so Polymorphism may be used to override the moveLeft() method, so that the posX attribute is decremented by 2 spaces.

Alternatively, you could define a specialMove() method, and have a subclass that completely changes the contents of the method, just keeping the same name.

Question 15

Chapter 68:

How is Polymorphism achieved?

Answer 15

By overriding methods.

By defining a method of the same name and parameters as the inherited method.

Question 16

Chapter 68:
Inheritance or Composition;
Which is preferable, and why?

Answer 16

Composition.

With Composition, you are not bound by the tree structure of Inheritance.

If you have a specific object [for example a robot dog] you would need to inherit certain methods and attributes from a subclass [dog might be a subclass of animal]. If you then don’t want your specific object to inherit from the superclass, you would have to either duplicate code, or give the specific object more methods than they need.

With Composition, you define the methods that you need, and then define your classes with access to certain methods.

Question 17

Chapter 68:

What are the 3 Access Modifiers / Access Specifiers?

Answer 17

Public
Private
Protected

Question 18

Chapter 68:

What is the Public Access Modifier / Access Specifier?

Answer 18

The member is accessible from outside of the class.

Question 19

Chapter 68:

What is the Private Access Modifier / Access Specifier?

Answer 19

The member is only accessible inside of the class.

Question 20

Chapter 68:

What is the Protected Access Modifier / Access Specifier?

Answer 20

The member is accessible within the class, and within subclasses.

Depending on the programming language, the member may or may not be accessible by classes in the same package.

Question 21

Chapter 68:

What is the structure of a Class Diagram?

Answer 21

1x3 table.

Name in the top.
Attributes in middle.
Methods at the bottom.

Public indicated by ‘+’
Private indicated by ‘-‘
Protected indicated by ‘#’

Question 22

Chapter 68:

What is an interface in OOP?

Answer 22

When multiple objects require the same set of methods, an interface could be used to collect all of the shared methods and then referenced as one call in the different objects.

For example
SwitchOn()
SwitchOff()
SetTimer(time)
GetTimer()
...

May be used by a microwave, a lighting system, a computer or many other objects. The listed methods could be placed in an interface called Switches, for example, and the objects could implement the interface, rather than repeating several method definitions.

Question 23

Chapter 68:

What are the advantages of Object-Oriented Programming?

Answer 23

The methodology forces designers to plan thoroughly, making for better designs with fewer weaknesses.

Once an object is created, knowledge of the implementation is not required for use. This is especially important for collaborative projects.

New objects, slightly different from others can be created easily.

Easier to maintain, as the structure is enforced.

Question 24

Chapter 68:

What are the disadvantages of Object-Oriented Programming?

Answer 24

It can be inefficient, as the structure can sometimes be more memory and CPU intensive than alternative methods.

Requires time and planning, which can slow down a project. This could lead to missing deadlines.

For less intensive projects, Object-Oriented structure can make the code look bloated, as efficiency may not be drastically improved, while complexity will drastically increase.

Question 25

Chapter 69:

What is a programming paradigm?

Answer 25

Different styles of programming.

Question 26

Chapter 69:

What are the 2 main types of Programming Paradigm?

Answer 26

Imperative.
    - Procedural.
    - Object-Oriented.
Declarative.
    - Functional.

Question 27

Chapter 69:

What are Imperative Programming Paradigms used for?

Answer 27

Imperative Programming Languages focus on how to execute. A series of steps is written to achieve a goal.

Question 28

Chapter 69:

What are Declarative Programming Paradigms used for?

Answer 28

Declarative Programming Languages focus on what to execute. Control flow is not defined by the programmer.

Question 29

Chapter 69:

What is a Procedural Programming Language?

Answer 29

Just a sequence of steps using sequence, selection, iteration, and recursion.

Question 30

Chapter 69:

What is an Object-Oriented Programming Language?

Answer 30

Objects with different properties (attributes) and functions (methods) are used to model a problem or situation.

Question 31

Chapter 69:

What is a Functional Programming Language?

Answer 31

Instead of having a program flow, functions are defined in reference to inputs.
Variables cannot be defined.

Question 32

Chapter 69:

What is a Function?

Answer 32

Entering a value (domain) will return an output (co-domain).

Entering the same value will return the same output. (Unless the function makes use of Random Number Generation).

Question 33

Chapter 69:

What is an example of a Functional Programming Language?

Answer 33

Haskell.

Question 34

Chapter 69:

Is SQL a Functional Programming Language?

Answer 34

No.

SQL is Declarative, but not Functional.

Question 35

Chapter 69:
‘Parameter’ and ‘Argument’ are often used interchangeably.
What is the distinction?

Answer 35

Arguments is a value or expression.

Parameter is a reference to the value or expression.

Question 36

Chapter 69:

What is the name of the process of giving particular inputs to a function?

Answer 36

Function Application.

Question 37

Chapter 69:

What is a First-Class Object?

Answer 37

An Object that can be:
assigned to a variable,
appear in expressions,
be assigned as an argument,
be returned in a function call.

Question 38

Chapter 69:
Functional Language functions are said to have no side effects.
What does this mean?

Answer 38

They cannot change the value of any object.

Question 39

Chapter 69:
What is Referential Transparency?
Why is it useful?

Answer 39

Where a function called with the same parameters will always return the same result.

It makes it easier for programmers to write bug-free programs. It makes the program more predictable.

Question 40

Chapter 69:

What is Function Composition?

Answer 40

When multiple functions are combined.

e.g.
f(g(x))

Question 41

Chapter 69:

How do you represent f(g(x)) in Haskell?

Answer 41

(g.f) {input}

Question 42

Chapter 69:

What are Types and Typeclasses in Haskell?

Answer 42

Types = sets of values.

Typeclasses = sets of types.

Question 43

Chapter 70:

What is a Higher-Order Function?

Answer 43

A function that takes another function as a parameter or returns a function as a result. (Or both).

Question 44

Chapter 70:

What are some examples of Higher-Order Functions?

Answer 44

Map, Filter, Fold(/Reduce).

Question 45

Chapter 70:
Haskell only takes one parameter at a time.
How does this work?

Answer 45

The program takes the first parameter and returns a new function where the first parameter has been evaluated.
The second parameter is then passed into the returned function.

This continues for all parameters.

Question 46

Chapter 70:

What is Partial Function Application?

Answer 46

Where you create a function that calls another function with a predefined parameter.
Partial Application is fixing/binding some inputs to a function to produce another more specific function.

e. g.
function: add

addSix = add

addSix 10
» 16

Question 47

Chapter 70:

What does the Map function do?

Answer 47

Map is a higher-order function that takes a function and a list as parameters.
Every item in the list is passed through the function and the results are stored to a new list. The new list is returned.

e. g.
function: Square x = x * x
list: Values = [1, 2, 3, 4]

Map(Square, Values)
» [1, 4, 9, 16]

Question 48

Chapter 70:

What does the Filter function do?

Answer 48

Filter is a higher-order function that takes a predicate function and a list as parameters.
Every item in the list is passed through the function. The function will return true or false. The returned value will be a sublist of all items that returned true.

e. g.
function: IsEven x = bool(x mod 2 == 0)
list: Values = [1, 2, 3, 4]

Filter(IsEven, Values )
» [2, 4]

Question 49

Chapter 70:

What is a predicate?

Answer 49

An expression which is either affirmed or denied.

Returns true or false.

Question 50

Chapter 70:

What does the Fold function do?

Answer 50

Fold is a higher-order function that takes a function, an initial value and a list of parameters.
The initial value and the first item in the list are combined using the function. This value is then combined with the next item in the list to give a new result. This passes through the whole list and returns a single value.

e.g.
foldL (+) 0 [2, 3, 4, 5]
» 14

Parenthesised as
(((0 + 2) + 3) + 4) + 5

foldL = fold left, i.e. start with the leftmost value.
foldR = fold right, i.e. start with the rightmost value.
[In this case the result would be the same as addition is commutative].

Question 51

Chapter 71:

What are the two parts to a List?

Answer 51

Head and Tail.
Head = first item in list.
Tail = every other item in list.

Question 52

Chapter 71:
What is the Head of a List?
What is the Tail of a List?

Answer 52

Head is the first element in the list.

Tail is a sublist of all the items in the list except for the head. (The rest of the list).

Question 53

Chapter 71:

What are the two main ways to add an item to a list?

Answer 53

Prepending = Add a new item to the front of the list.

Appending = Add a new item to the back of the list.

Question 54

Chapter 72:

What is Big Data?

Answer 54

When you have so much data that traditional methods of organisation and analysis can no longer be viably used.

Question 55

Chapter 72:

What are the 3 parts to Big Data?

Answer 55

Volume (Size),
Velocity (Access Latency),
Variety (What the data can be).

Question 56

Chapter 72:

What does Big Data allow us to do?

Answer 56

Detect and Analyse relationships in a field.

Question 57

Chapter 72:

How is Big Data used in Healthcare?

Answer 57

Doctors can collect data such as symptoms, or blood pressure, on patients and compare the data to others to try and diagnose problems and find solutions.

Question 58

Chapter 72:

*How much data does Google process every day?

Answer 58

20 Petabytes.

Question 59

Chapter 72:

*How many search queries does Google receive every day?

Answer 59

3 Billion.

Question 60

Chapter 72:

How did Google help health officials in 2009?

Answer 60

During an outbreak of H1N1, Google was able to identify its spread far more quickly that government statistics.

Question 61

Chapter 72:

How does Amazon use Big Data?

Answer 61

To improve book recommendations.

A conventional method would be to look at a book’s metadata and search for other books that are similar, but this isn’t optimal as if, for example, you wanted to read a book about how to program in python, you are unlikely to want another book about the same topic.

Amazon used Big Data to see, given a book, selecting people who have read that same book, what else they read and enjoy.

Question 62

Chapter 72:

What is the Fact-Based Model?

Answer 62

An alternative to the Relational Data Model.

Fact-Based Model records immutable facts with timestamps. This means that previous data cannot be changed, but new data can be used instead.

Question 63

Chapter 72:

What is Graph Schema?

Answer 63

Where data is stored as nodes and relationships, and both nodes and relationships have properties.

Question 64

Chapter 72:

What makes Graph Schema better than Relational?

Answer 64

If, for example, you want to search a network of people for people that are friends with Steve:

In a Relational Database, you would need to search the whole database for everyone that has Steve as a friend.

In Graph Schema, you only need to locate Steve, as observe the relationships.

Finding friends-of-friends would be impractical in a large Relational Database.