4.12 Fundamentals of Functional Programming

Question 1

Main Features of Functional Programming (6)

Answer 1

• Functions used as building blocks
• Statements written as a series of functions
• Each accepts input data as arguments and returns an output
• Statelessness and immutability
• • Can’t overwrite/edit
• All can do is perform cals + return a value
• Inputs/outputs can be values or functions

Question 2

Benefits of Functional Programming (4)

Answer 2

• Easy to write, understand, predict behaviour
• Less prone to bugs as no overwriting/editing
• Allows parallel processing
• • Data can’t be altered by previous function so no worries about execution order
• • More than 1 processor can work on different parts of large data set at once
• • Won’t affect any other part of data
• Helps deal with big data

Question 3

A First Class Object is one that may (4)

Answer 3

• Be assigned to a variable
• Appear in an expression
• Be assigned to an argument
• Be returned in a function call

Question 4

Function Application (2, Example)

Answer 4

• Process of giving particular inputs to a function
• Apply/call function by using name followed by argos needed separated by spaces

addThreeInputs(x, y, z) = x + y + z
Integer → Integer → Integer → Integer ( x → y → z → output)

Question 5

Partial Function Application (3, Example)

Answer 5

• Uses a function + applies it partially with another argument
• Reduces num of args passed to function
• Can perform multiple times to further reduce

E.g. Area(A,B) → AB
Partially apply Area to the arguments 3 & 5:
Area5(A) → A5 (only need to apply 1 argument)

Question 6

Composition of Functions (1, Example)

Answer 6

• Process results in combining two functions to get a new function

E.g. f: A → B f(x) = x + 2
g: B → C g(x) = x2
Function: g𐩑f = (x+2)2
Domain = A, Co-Domain = C

Question 7

Function (definition)

Answer 7

A rule that for each element of some set A of inputs, assigns an output from a chosen set B but without necessarily using every member of set B

Question 8

Domain and Co-Domain (definition) (1)

Answer 8

• Domain = set of inputs
• Co-Domain = set of outputs
• Can have different set/data types of domain & co domains

Question 9

Higher Order Functions (definition)

Answer 9

• Takes a function as an arg or returns a function as a result or both

Question 10

MAP (def, recursion process, example)

Answer 10

• Applies given function to each element in list and returns a list
  Recursive: take Head of list, apply function, recursive through Tail
• E.g. Square(x) = x2
• Map Square([4, 7, 1, 2]) Outputs: [16, 49, 1, 4]

Question 11

FILTER (def, example)

Answer 11

• Processes a data structure to produce new structure containing exactly elements of original that match a given condition
• E.g. Filter(>10): [8. 9, 10, 11, 12] Outputs: [11, 12]

Question 12

FOLD OR REDUCE (def, example)

Answer 12

• Reduces list of values to single value by repeatedly applying a combining function to list
• E.g. Fold 1 (+) [4, 7, 9, 1] Outputs: 1+4+7+9+1: 22

Question 13

Head and Tails (4)

Answer 13

• Head: Tail
• The Head is always a value
• The Tail is always a list
• Can use head and tail to write functions that use recursion