2. We’re slowly working our way towards classes and objects
More Data Structures
We’re slowly working our way towards classes and objects
Before that, we have two more data structures to look at
Enumerations
Structs

3. Enumerations Enumerations let us create integral constants with names
Also known as enums
Useful for creating finite sates or values in a program
Such as the state of an enemy
Calm, Alert, Chasing
Can then use branching to change AI based off state

4. Enumerations (1) We define enumerations using the enum keyword
Followed by a name for that enum
We can then enter in lots of names
As many as we want
For the possible values
Both the name of the enum and the values inside them should use first-capital-letters

5. Use the name of the enum as the data-type of the variable
Enumerations (1)
We can then create a variable
That stores one of the enum’s values
Use the name of the enum as the data-type of the variable

6. We use one of the values in the enum
Enumerations (1)
We use one of the values in the enum
As the value for the variable
That’s all we do!
We type in the name of the value
We don’t type in the name of the enum

7. Enumerations (1) Ex Create a new empty C++ solution
Add the main() function to it
Make it return 0
Create an enum for the suits of a deck of cards
Add one value for each suit
Output each of these values to the console
What values are output?

8. When we output the values of the enum, we saw integers
Enumerations (2)
When we output the values of the enum, we saw integers
Starting at 0
Going up to 3
We mentioned this, but enum values are integral constants

9. Enumerations (2) A constant is a value that can’t change
The values in an enum have a set integer value they ‘represent’
We can
change the value they ‘represent’
convert between integers and enum values

10. We can only use integer values
Enumerations (2)
Let’s look at changing the integer value they represent
Really easy to do
Add an equal sign after the enum value
Then enter what we want it to be
We can only use integer values

11. Enumerations (2)
When we run this we can see the new values we used in the console

12. Enumerations (2)
Although we’re free to change these values, we need to think carefully
About two things
Why we want to change them (the default values often work fine)
What to change them to
These will depend on the program we’re making

13. Enumerations (2) Ex
Change your enum values so they use different integer values
Make sure they are output to the console
Run your program and check that they now use the new values

14. Enumerations (3)
We mentioned that we can convert between enum values and integers
From enum to integer is implicit
We only need to store the enum value in an integer variable
From integer to enum value is explicit
We need to run a function to handle the conversion

15. Enumerations (3) We have to use the static_cast function
Uses angular brackets
Contain the data-type to convert to
Then circular brackets
Contain the value to convert

16. Structs We then have structs
They act like classes, in that they can have
properties
functions
They can even use inheritance!

17. Structs
While there is not much difference between a class and a struct, there is a difference in practice
We should only use structs for “Plain-Old Data” types
That only contain data
And don’t contain functions
This is a suggested use, and not a requirement

18. For example, we could use a struct to represent a ‘Card’
Structs
For example, we could use a struct to represent a ‘Card’
It has a suit
It has a value
But doesn’t do anything

19. Structs (1)
We can create a struct using the struct keyword
Then give it a name

20. We don’t have to give them values
Structs (1)
We can give this struct variables
Where specific data is stored
We simply make variables as per norm
We don’t have to give them values
Or use public/private

21. Create a struct for a ‘Card’
Structs (1) Ex
Create a struct for a ‘Card’
Make it outside any scope
Give it two variables
A Suit
A value

22. Structs (2) We can then make a variable using this struct type
We don’t give it a value
Simply declaring the variable is enough
We won’t get null pointer exceptions

23. Structs (2) From here, we can give the struct values
By accessing the variables in it
Note that we can’t output a struct as-is
We need to output their individual variables

24. Structs (2) Ex
Try creating a Card value in the main()
Give this struct values for the Suit and value
Output this struct to the console

25. Struct Practice (1) Ex
To get some practice with structs, create the following program
Create an array of Card values (52, to be exact)
Use some clever maths to give each card
The correct suit (you may need to use conversion here)
The correct value

26. Struct Practice (2) Ex Once created, output each card to the console
In the form “Jack of Hearts”
See the example output

27. Create a separate function that shuffles the array of Cards
Struct Practice (3) Ex
Create a separate function that shuffles the array of Cards
Run the function, and output the array of cards afterwards
To make sure it is shuffled

28. Struct Practice (4) Ex
Create a function that sorts the cards in a specific order
First in order of suit (Hearts  Diamonds  Clubs  Spades)
Then in order of value
Run this function on your array after shuffling it
Then output it
Make sure they are in the correct order now

29. Struct Practice (5) Ex
Make a function for playing a game of Red or Black
Takes an array of Cards
Starts by showing the first Card in the array
Then asks user if the next one is red or black
If they get it right, they get a point and move on to the next card
If they get it wrong, output their score and end the function

30. Make a struct that represents a Point in 2D space
Struct Practice (6) Ex
Make a struct that represents a Point in 2D space
With x and y coordinates
Make a function that takes two structs
And calculates the distance between them
Use Pythagoras’ Theorem to do this

31. Struct Practice (7) Ex Make a function that takes two parameters
An array of Points
A single Point
This function should return the shortest distance found
Between the lone Point
And the Points in the array

32. END OF UNIT!