Functors and lambda expressions

Question 1

What are functors?

Answer 1

Functions with state

Question 2

Why do we want functors?

Answer 2

• Allow more generic code
• Contains state
• Can be passed as arguments to stand library containers

Question 3

What are lambda expressions?

Answer 3

Anonymous functors, functors that are not explicitly named or identified. Useful for simple cases

Question 4

What does the auto keyword?

Answer 4

Gets the compiler to determine the best possible type to use in the context it is given

Question 5

When should we use lambda?

Answer 5

• To provide type-specific details to generic implementations of algorithms (e.g. sorting comparators)
• To provide type-safe macros to inline-able equations
• Use them with standard library algorithms

Question 6

When should we not use lambda’s?

Answer 6

-Instead of proper function calls.
- When they need to be stateful

Question 7

What does the inline function do?

Answer 7

Used for compiler optimisation, substitutes all functors calls to the item in the return statement.

Question 8

What is a stateful functor?

Answer 8

Functor with state

Question 9

What does this line of code imply:
auto plusFive = -> int {}

Answer 9

This is a lambda expression that takes an int x and returns an int.
Should be: [] (int x) -> int {}

Question 10

For lamba expressions how do we capture all the variables of a file?

Answer 10

By putting “=” in the rectangular brackets: [=]

Question 11

Does lambda need to capture the this pointer in classes?

Answer 11

No it is automatically captured.