Pure Functions

Pure Functions

In this lesson — part of Functional Foundations — you'll learn pure functions in Dart and why it matters in real work.

Why it matters

Functional style — pure functions and immutability — makes code easier to test and reason about.

Key ideas

• Pure functions
• Immutability
• No shared mutable state
• Predictable outputs

In practice

Here's how it looks in idiomatic Dart:

int square(int x) => x * x; // pure: no side effects, output depends only on input

void main() {
  print(square(5)); // 25
  print(square(5)); // 25, always identical
}

Dart note: Dart treats functions as first-class values, so a pure top-level function like this can be passed around and reused freely.

Try it yourself

Exercise: In Dart, rewrite a function that mutates a global so it's pure.

Recap

You now understand pure functions and can apply it in Dart. Mark this lesson complete and continue to the next one.