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

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

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

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

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

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?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

END OF UNIT!