Pure Functions and Side-Effect-Free Design
Writing functions that always return the same output for the same input.
Welcome
Pure functions always produce the same output for the same input and cause no side effects. They are the building block of functional programming in Swift.
Definition of a Pure Function
A function is pure if:
• Same input always yields same output
• No observable side effects (no mutations, I/O, global state)
```swift
func add(_ a: Int, _ b: Int) -> Int { a + b } // pure
```
All lessons in this course
- Pure Functions and Side-Effect-Free Design
- Higher-Order Functions: map, flatMap, compactMap
- Function Composition and Pipelines
- Lazy Sequences for Efficiency