Closures & Iterators

Closures and iterators are Rust’s core functional-style tools for local behavior customization and lazy sequence processing with low-level performance.

Concepts

• Closures
• Closure Type Inference
• Capturing the Environment
• Fn, FnMut, FnOnce
• move Closures
• Iterators
• The Iterator Trait
• Iterator Adapters
• Consuming Adapters
• Lazy Evaluation
• Zero-Cost Abstractions

Patterns

• Prefer Iterator Pipelines to Manual Indexing
• Return Iterators Instead of Collecting

Antipatterns

• Unconsumed Iterator Adapters
• Moving Out of FnMut Closures
• Manual Index Loops for Speed

Related Existing Notes

Function Pointers · Returning Closures · Boxed Closure Returns · Unnecessary Collect · While and For Loops · Needless Clone · Ownership · Borrowing

Sources

• The Rust Programming Language, ch. 13 “Functional Language Features: Iterators and Closures” - the-book, https://doc.rust-lang.org/book/ch13-00-functional-features.html
• The Rust Programming Language, ch. 13.1 “Closures” - the-book, https://doc.rust-lang.org/book/ch13-01-closures.html
• The Rust Programming Language, ch. 13.2 “Processing a Series of Items with Iterators” - the-book, https://doc.rust-lang.org/book/ch13-02-iterators.html
• The Rust Programming Language, ch. 13.4 “Comparing Performance: Loops vs. Iterators” - the-book, https://doc.rust-lang.org/book/ch13-04-performance.html