Functional Programming in Rust: From Basics to Advanced Patterns

The book "Functional Programming in Rust" is a practical guide that will help you master the paradigm of functional programming in the context of one of the most performant and safe modern languages. The author, Alexey Vorontsov, an experienced developer in Rust and Haskell, consistently guides the reader from basic concepts to complex compositional patterns, showing how to make Rust code more predictable, testable, and concise.

What is this book about?

• FP Basics in Rust: pure functions, data immutability, absence of side effects, and working with ownership in a functional style.
• Closures and Iterators: a deep dive into closures, iterators, and adapters (map, filter, fold, flat_map). You will learn to build data transformation chains without loops.
• Algebraic Data Types: using enum and Option/Result for modeling states and error handling without exceptions — in the spirit of Maybe and Either monads.
• Functors, Applicatives, and Monads: implementing and applying these abstractions in Rust. You will learn how the "monad" pattern helps manage side effects and asynchrony.
• Composition and Currying: techniques for creating higher-order functions, partial application, and composition to build complex logic from simple building blocks.
• Lazy Evaluation and Infinite Structures: how to use iterators for lazy processing of large data volumes and modeling infinite sequences.
• Testing and Debugging: writing unit tests for pure functions, using property-based testing (proptest), and debugging functional code.

Who is this book for?

• Intermediate Rust developers who want to go beyond the imperative style and write more elegant code.
• Programmers familiar with FP (Haskell, Scala, Clojure) who want to apply their knowledge in Rust.
• Engineers working on high-load systems — the functional approach simplifies concurrency and reduces the number of bugs.
• Students and researchers studying modern programming paradigms.

What will you learn?

After reading the book, you will be able to:

• Write functions that do not modify external state and are easy to test.
• Efficiently use iterators and closures for processing collections without loops.
• Build safe data processing pipelines using combinators (and_then, map, or_else).
• Implement your own monadic structures for context management (e.g., logging, configuration, operation cancellation).
• Apply currying and partial application to create reusable functions.
• Design application architecture based on composition rather than inheritance.
• Use tools like rayon for parallel data processing in a functional style.

The book contains numerous code examples, exercises, and practical projects (from a JSON parser to a simple web server based on functional principles). All examples are relevant for the latest stable versions of Rust (edition 2021+).