0Pricing
Swift Academy · Lesson

Map/Filter/Reduce, lazy sequences

Use map / filter / reduce to transform, select, and combine; then add .lazy to defer work and avoid intermediate arrays.

Core idea

Core algorithms:

  • map: transform each element
  • filter: keep elements matching a predicate
  • reduce: combine into one value
  • .lazy: defer work to avoid temporary arrays

map

map transforms each element and returns a new array.

let nums = [1, 2, 3]
let doubled = nums.map { $0 * 2 }        // [2, 4, 6]
print(doubled)

let words = ["swift", "kit"]
let upper = words.map { $0.uppercased() } // ["SWIFT","KIT"]
print(upper)

All lessons in this course

  1. Sequence/Collection hierarchies
  2. Map/Filter/Reduce, lazy sequences
  3. Custom iterators & performance tips
← Back to Swift Academy