Lazy collections for performance in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a lazy collection from an array.

Swift

let numbers = [1, 2, 3, 4, 5]
let lazyNumbers = numbers.[1]

Drag options to blanks, or click blank then click option'

Alazy

Bmap

Cfilter

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Using map or filter directly creates eager collections.

Using lazy creates a lazy collection that delays computation until needed.

2fill in blank

medium

Complete the code to lazily map numbers to their squares.

Swift

let numbers = [1, 2, 3, 4, 5]
let squares = numbers.lazy.[1] { $0 * $0 }

Drag options to blanks, or click blank then click option'

Afilter

Bmap

Creduce

DcompactMap

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter instead of map.

The map function transforms each element, and combined with lazy, it delays the computation.

3fill in blank

hard

Fix the error in the code to lazily filter even numbers.

Swift

let numbers = [1, 2, 3, 4, 5]
let evens = numbers.[1].filter { $0 % 2 == 0 }

Drag options to blanks, or click blank then click option'

Alazy

Bmap

Cfilter

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Calling filter directly without lazy causes eager evaluation.

You must call lazy before filter to make the filtering lazy.

4fill in blank

hard

Fill both blanks to lazily map numbers to strings.

Swift

let numbers = [1, 2, 3, 4, 5]
let strings = numbers.[1].[2] { "Number: \($0)" }

Drag options to blanks, or click blank then click option'

Alazy

Bmap

Cfilter

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping map and lazy or missing lazy.

First call lazy to delay operations, then map to transform elements.

5fill in blank

hard

Fill all three blanks to create a lazy collection that filters numbers greater than 3, maps them to strings, and then collects the results.

Swift

let numbers = [1, 2, 3, 4, 5]
let result = Array(numbers.[1].[2] { $0 > 3 }.[3] { "Value: \($0)" })

Drag options to blanks, or click blank then click option'

Alazy

Bfilter

Cmap

Dreduce

Attempts:

3 left

💡 Hint

Common Mistakes

Using reduce instead of map or missing lazy.

Use lazy to delay, then filter to select, and map to transform.