Functional programming

Question 1

What type of functions does functional programming use?

Answer 1

Pure functions (Do not modify data, do no use variables, no function shares data with any other function)

Question 2

What is functional programming useful for?

Answer 2

• Machine learning

- Processing big data

Question 3

Name some higher order Haskell functions

Answer 3

• map
• filter
• fold

Question 4

In (f: A → B), what part is the domain?

Answer 4

A

Question 5

In (f: A → B), what part is the codomain?

Answer 5

B

Question 6

Declared values or expressions are immutable. What does immutable mean?

Answer 6

Immutable means that they can’t be changed during program execution.

Question 7

Name some examples of base types in Haskell (must be written with a capital)

Answer 7

• Integer
• Float
• Double
• Bool
• Char

Question 8

What class object is a function?

Answer 8

A function is a first class object which can be an argument to another function as well as the result of another call.

Question 9

What is function application?

Answer 9

Applying a function to its arguments

Question 10

What is partial function application?

Answer 10

Applying part of a function to its arguments, splitting them up using brackets.

Question 11

What is composition of functions?

Answer 11

Combining two functions together (indicated using a small circle ∘)

Question 12

What is required for function composition to work?

Answer 12

The codomain of f must match the domain of g

g ∘ f: A -> C

Question 13

How is function composition represented in Haskell?

Answer 13

(A.B)

Question 14

What is a higher order function?

Answer 14

a function that takes one or more functions as arguments and/or returns a function as its result. (map, filter, fold)

Question 15

What does the ‘map’ higher order function do in Haskell?

Answer 15

Applies a function to every element in the list.
> map (^2) [20, 3, 51, 6, 3, 7]
[400, 9, 2601, 36, 9, 49]

Question 16

What does the ‘filter’ higher order function do in Haskell?

Answer 16

Filters a list based on criteria.
> my_list = [1,2,3,4,5,6,7,8,9]
> filter (>5) my_list
[6,7,8,9]

Question 17

What does the ‘fold’ higher order function do in Haskell?

Answer 17

Adds each element in the list from left to right (or right to left depending on if the command is foldl or foldr)
> my_list = [1, 2, 3, 4]
> foldl (+) 0 my_list
10

Question 18

What is the head of a list?

Answer 18

The number at the start

Question 19

What is the tail of a list?

Answer 19

Every number which isn’t the head

Question 20

How do you find the length of a list in Haskell?

Answer 20

Input: length [1,2,3]
Output: 3

Question 21

How do you reverse a list in Haskell?

Answer 21

reverse xs

Question 22

How do you get the Nth element out of a list in Haskell?

Answer 22

xs !! n

Question 23

How do you prepend an element to a list in Haskell?

Answer 23

: