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Book Overview & Buying
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Table Of Contents
Design Patterns and Best Practices in Rust
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Closures (also called lambda functions or anonymous functions) are functions that capture variables from their surrounding scope. Unlike regular functions, a closure can "remember" values that existed when it was created, carrying that state wherever it goes. This makes them powerful for callbacks, deferred execution, and creating specialized behavior at runtime.
Closures originated in Lisp in 1958, making them one of the oldest concepts in programming language design. This long history means closure patterns have been refined over decades. Functional languages have used closure-based patterns for configuration, callbacks, and higher-order functions for decades. Languages such as Scheme, Haskell, OCaml, JavaScript, and many others have developed sophisticated patterns around closures.
What makes Rust's closure implementation unique is how it integrates with the ownership system. Rust has three closure traits: Fn, FnMut, and FnOnce. These...