C++

Question 1

How should one always give arguments to a function if possible?

Answer 1

as const reference

Question 2

one line if statement

Answer 2

“expression” ? “command if true” : “command if false”

Question 3

what should you always check when creating new functions?

Answer 3

const correctness

Question 4

what is a static member variable?

Answer 4

A variable which belongs not to the instance but to the class -> multiple instances access the same value

Question 5

what is :: called?

Answer 5

scope resolution operator -> then searches global namespace

Question 6

If you do not specify the access modifier in a class, are it’s members private, protected or public?

Answer 6

private

Question 7

what is a std::map?

Answer 7

A container, that stores key-value pairs. Keys must be unique (otherwise the old entry is overwritten). A map is sorted through the keys through the < operator, which can also be provided.

Question 8

what are std::vector and std::list?

Answer 8

both are containers
vector: elements in one block of memory, easy to add and remove elements at end, not so easy to insert, …
list: indirect adressing -> good for insertion, slower for iteration

Question 9

what important std containers are there?

Answer 9

vector, list, map, multimap, queue, stack, deque, set, array, …

Question 10

what is the extern keyword?

Answer 10

it says, that a variable is defined in another translation context

Question 11

how does one define a C++ macro?

Answer 11

define “macroname” “code”

• not recommended in modern C++

Question 12

How do I declare a variable that stores the address of another?

Answer 12

varA = &varB;

Question 13

what is * called in C++? How can it be read?

Answer 13

Dereference operator
“value pointed to by”

Question 14

what is & called in C++? How can it be read?

Answer 14

2 meanings:
1. Address-of operator when used in expression
“address of”
2. In declaration: part of identifier, denotes a reference
“is a reference to”

Question 15

How does one declare a reference in C++?

Answer 15

“type” & “reference name” = var;

Question 16

what is the difference between a pointer and a reference?

Answer 16

• reference is a “const pointer”. It is initialized at declaration and the addres it points to cannot be changed.
• it is dereferenced implicitly, so no * is needed

Question 17

What is pass-by-value/reference?

Answer 17

a pass by value function takes an input object and makes a copy of it, thus not changing the objects value.
pass by reference takes a reference and thus operates on the original object.

Question 18

What does the declaration of a pass-by-reference function look like? How is it called?

Answer 18

typeA func(typeB & a){…}

typeB b = …;
func(b)

Question 19

When should objects be initialized? And why?

Answer 19

Always upon declaration to omit undefined behaviour

Question 20

Should one initialize members as declaration in the constructor or in the initialization list?

Answer 20

Always in the initialization list

Question 21

In a switch, if multiple statements shall execute the same code, how does one do it?

Answer 21

case a:
case b:
{
shared code…
} break;

Question 22

what does mutable/immutable mean in C++?

Answer 22

immutable means not changeable (const). Mutable is a keyword that can be applied to a field of a const object, which reverts it’s immutability

Question 23

which function converts const char to int? (e.g. for input args)

Answer 23

atoi()

Question 24

what is the difference between
CParid testParid = getUpdatedParidFromFile();

and
CParid testParid;
testParid = getUpdatedParidFromFile();

Answer 24

the first uses the copy constructor, while the second uses the = operator

Question 25

how does one define a lambda function?

Answer 25

“type” name = [“capture clause”] (“arguments”) -> “explicit return type (optional)”{ “function body”}

Question 26

How can I define a function in a .h file?

Answer 26

By using the inline keyword. Otherwise the linker will load it multiple times if applicable

Question 27

How is an R-value reference written

Answer 27

&&

Question 28

When should a virtual destructor be used? And when not? why?

Answer 28

Polymorphic base classes should have a virtual destructor. Final classes should NOT!
If a polymorphic base class does not have a virtual destructor, only the child classes destructor is called upon deletion, leading to a memory leak (where the “base class part” does not get deleted)
If a final class has a virtual destructor (or any virtual function), additional overhead (virtual table) is created.

Question 29

When creating an empty class, which methods are created automatically?

Answer 29

Constructor
Copy Constructor
Destructor
Copy Assignment Operator

Question 30

When is no default copy constructor, destructor or copy assignment operator created?

Answer 30

If the logic doesn’t make sense. I.e. if a member is a reference, reassignment doesn’t work. Or if the class has a base class with private destructor, since the default destructor want’s to call the base’s

Question 31

how does one declare a function, that takes a function as an argument?

Answer 31

type functionName(std::function<return type(input type)> name)

Question 32

how can a function that takes an argument be called without arguments?

Answer 32

If default arguments are defined or it is overloaded

Question 33

What is the difference between heap and stack memory? How are variables allocated there?

Answer 33

Stack: very quick, follows call stack. Value type initialization writes there. Deleted when scope ends (by moving memory pointer back)
Heap: accessible from outside of scope and not in order. Reference types (new keyword) a lot of overhead. Danger of garbage.
Always use stack if possible

Question 34

Does static write variables into stack or heap?

Answer 34

Non of those. Static is it’s own memory segment

Question 35

what is the difference between const_iterator and iterator?

Answer 35

const iterator doesn’t allow you to change the values it points to