Enums and Structs

Question 1

Program defined type / User defined type

give definition, examples and rules

Answer 1

A custom type we can create for use in our own programs.

The enumerated types and class types (including structs, classes and unions) allow for creation of program defined-types.

Program defined types must be defined before they are used

Question 2

Type definition
Exempt from?

Answer 2

The definition of a program defined type. They are exempt from the one-definition rule

Question 3

Enumeration / Enumerated Type / Enum

Answer 3

a compound data type where every possible value is defined as a symbolic constant

enumerations are distinct types, meaning the compiler can differentiate them from other types (unlike type aliases)

Question 4

Name for the symbolic constants inside an enum

Answer 4

enumerator

Question 5

Unscoped enumerations

Answer 5

they put their enumerator names in the same scope as the enumeration definition itself (as opposed to creating a new scope region like a namespace does).

Will implicitly convert to integral values

Question 6

scoped enumerations

Answer 6

similar to unscoped enumerations but

won’t implicitly convert to integers

enumerators are only placed into the scope region of the enumeration (not into the scope region where the enumeration is defined)

Question 7

struct

Answer 7

program defined data type that allows us to bundle multiple variables together in a single type.

Question 8

data members / member variables

Answer 8

variables that are part of a struct or class

Question 9

member selection operator

Answer 9

operator.

allows you to access a specific member variable for structs or refs to structs

Question 10

member selection from pointer operator

Answer 10

operator->

allows you to access a specific member variable for pointers to structs

Question 11

aggregate data type / aggregate

Answer 11

any type that can contain multiple data members

arrays and structs with only data members

Question 12

aggregate initialisation

Answer 12

directly initialises members of aggregates with list of comma seperated values

e.g.

Triad t { 1, 2, 3 };

Initialises each member of the struct in order of declaration

Question 13

memberwise initialization

Answer 13

each member in the struct is initialized in the order of declaration.

Question 14

Designated initializers

Add a code example here

Answer 14

C++20

allow you to explicitly define which initialization values map to which members. The members must be initialized in the order in which they are declared in the struct, otherwise an error will result

Car myCar = { .make “Toyota”, .year = 2020 };

Question 15

non-static member initialization

Answer 15

When we define a struct (or class) type, we can provide a default initialization value for each member as part of the type definition

Question 16

default member initializer

Answer 16

name of default values passed to members in structs during non-static member initialization

Question 17

What will the compiler do to structs for performance

Answer 17

add padding. So the size of a structure may be larger than the sum of its members

Question 18

class template

Answer 18

a template definition for instantiating class types (structs, classes, or unions)

Question 19

Class template argument deduction (CTAD)

Needs code example

Answer 19

C++17 feature that allows the compiler to deduce the template type arguments from an initializer.