13.9 Summary

Iterators in Rust offer a clear and efficient way to process data. By separating how items are retrieved from what is done with them, Rust encourages declarative, readable code while retaining the performance of low-level loops.

  • Iterator Trait: Supplies items via the next() method.
  • Ownership Modes: Choose between immutable (iter()), mutable (iter_mut()), or consuming (into_iter()) iteration.
  • Adapter vs. Consumer: Adapters (e.g., map(), filter()) are lazy and return new iterators, while consumers (e.g., collect(), sum()) exhaust the iterator to produce a final result.
  • Custom Iterators: Implement Iterator on your structs to extend Rust’s iteration to any data structure or traversal pattern.
  • Advanced Concepts: Double-ended iteration, fused iterators, and short-circuiting can further refine performance and code clarity.
  • Zero-Cost: Compiler optimizations generally reduce iterator-based code to the same machine code as a hand-written loop.

By mastering Rust’s iterator abstractions, you’ll be well-equipped to write safe, concise, and performant code for a wide variety of data-processing tasks. Future chapters will build on these concepts as we delve into more advanced data handling.