1. Structures
December 6, 2017

2. Structures
Suppose you want to make a program to keep track of some basic information about every student at THS:
Name
Date of birth
State ID
GPA
Now consider how many variables you would need to do this (hint: a lot).
Isn’t there an easier way????
Create a structure!

3. Structures
A structure is a collection of variables of different data types under a single name.
It may help to think of a structure as an array with different data types.
In reality, structures are significantly more nuanced, but we will largely be using them in this way.

4. Structures The following syntax is used to declare a structure:
struct Date {
int month;
int day;
int year;
string day_of_week; };
Note the semicolon after the closing curly brace!

5. Structure Syntax
struct Date {
int month;
int day;
int year;
string day_of_week; };
This syntax declares a structure with name Date. Every Date in turn has four “sub-variables”: month, day, year, and day_of_week.
These “sub-variables” are known as member variables.

6. Structure Syntax
The following will declare three variables of type Date:
Date yesterday, today, tomorrow;
Each of these three variables has four member variables: month, day, year, and day_of_week.
It may help to think of this as creating three “mixed arrays” with four entries in each: month, day, year, and day_of_week.

7. Structure Syntax To access a member variable, use the dot operator:
yesterday.month = 12;
yesterday.day = 5;
yesterday.year = 2017;
yesterday.day_of_week = "Tuesday";
This can also be done using curly braces, like with an array:
Date yesterday = {12, 5, 2017, "Tuesday"};

8. Structure Syntax For today, the syntax is (essentially) the same:
today.month = 12;
today.day = 6;
today.year = 2017;
today.day_of_week = "Wednesday";
Using a single line:
Date today = {12, 6, 2017, "Wednesday"};

9. Structure Syntax Consider the following syntax:
today = tomorrow;
This is equivalent to the following:
today.month = tomorrow.month;
today.day = tomorrow.day;
today.year = tomorrow.year;
today.day_of_week = tomorrow.day_of_week;

10. Structure Syntax struct Date { int month; int day; int year; };
struct PersonInfo
double height;
int weight;
Date birthday;

11. Structure Syntax Consider the following syntax:
ShoeType shoe1, shoe2;
shoe1.style = 'A';
shoe1.price = 9.99;
cout << shoe1.style << " $" << shoe1.price << endl;
shoe2 = shoe1;
shoe2.price = shoe2.price / 9;
cout << shoe2.style << " $" << shoe2.price << endl;
Assuming style is a char and price is a double, what is the output?

12. Structure Syntax
Answer:
A $9.99
A $1.11