دانلود کتاب برنامه‌نویسی تابعی کاربردی در اسکالا (Scala)

Functional programming has steadily evolved from a theoretical curiosity into a practical and powerful paradigm for building modern software systems. With the growing complexity of applications and the increasing need for reliability, concurrency, and maintainability, the core tenets of functional programming, immutability, pure functions, composability, and type-safety have become more relevant than ever. This book is a comprehensive journey through the principles, patterns, and tools that empower developers to build robust and scalable applications using functional programming in Scala. The book begins by laying the theoretical foundations of functional programming, introducing concepts like pure functions, higher order functions, and immutability. It builds on these ideas with an exploration of category theory, showcasing its importance as a mathematical backbone for functional abstractions such as monads, functors, and applicative functors. We then transition into hands-on Scala development, covering the language’s features, Cats and ZIO libraries, and their use in managing side effects in a principled way. The chapters lead readers through advanced functional patterns, the use of optics, and the implementation of realworld systems using web frameworks such as http4s, Tapir, and ZIO HTTP. Each chapter builds on the previous one, ultimately guiding the reader in developing functional web applications that are composable, testable, and scalable. This book is designed for developers who want to take their knowledge beyond theory and apply functional programming techniques to address real-world software challenges. Ultimately, theory and practice converge in a comprehensive case study that integrates all previously learned tools and techniques. A functional toy e-commerce application is designed and implemented from scratch, covering everything from user registration and product catalog to order management, security, and analytics. Architectural diagrams, service design patterns, database schemas, and API endpoints offer a complete view of how functional programming principles are applied to a realworld system. Chapter 1: Fundamentals of Functional Programming – This chapter introduces the fundamentals of functional programming, rooted in lambda calculus, and contrasts it with imperative and object-oriented paradigms. It covers core principles like pure functions, immutability, and lazy evaluation. Using Scala, it highlights function composition, modularity, and benefits like testability, concurrency, and code predictability in real-world applications. Chapter 2: Implementation of Category Theory – This chapter presents category theory as the mathematical foundation for structuring functional programming concepts. It explains categories as collections of objects and morphisms with properties like identity and associativity. Core abstractions such as semigroups, monoids, functors, applicative functors, and monads are covered, along with practical types like reader, writer, and state. The chapter also introduces optics for precise data manipulation, linking theory to real-world functional programming in Scala. Chapter 3: Introduction to Scala – This chapter introduces Scala, a statically-typed language on the Java Virtual Machine that blends object-oriented and functional programming. It covers Scala’s functional features such as higher order functions, lambda expressions, closures, currying, and partial application. Readers learn about Scala installation, integrated development environment setup, version differences, and functional error handling with Option, Try, and Either. The chapter emphasizes treating functions as first-class citizens and Scala’s alignment with functional programming principles. Chapter 4: Understanding Cats – This chapter explores the Cats library, a powerful Scala toolkit grounded in category theory to support functional programming. It introduces core type classes like functor, monad, applicative, and traverse for modular, reusable code, along with advanced abstractions like contravariant and bifunctor. It covers semigroup, monoid, comonads, and useful data types like Validated and Writer, emphasizing Cats role in creating composable, type-safe, and effect-safe functional applications. Chapter 5: Understanding ZIO – This chapter introduces ZIO library, a type-safe, purely functional framework for building concurrent, asynchronous, and testable Scala applications. It explains ZIO’s core type, effect aliases, control flow, structured error and resource management, and concurrency with fibers and STM. Features like ZLayer for dependency injection and zio.test for effectful testing are highlighted, showcasing ZIO’s power in creating scalable, modular, and maintainable applications. Chapter 6: Effects Implementation in Pure Way – This chapter clarifies the difference between effects and side effects, highlighting the challenges side effects pose to functional purity. It explores strategies for managing them using pure functions, immutability, and abstractions like monads. Libraries like Cats Effect and ZIO offer tools for safe, type-safe I/O and exception handling. Practical examples demonstrate building scalable, maintainable applications by isolating side effects through functional design principles. Chapter 7: Functional Pattern Implementation – This chapter covers functional design patterns for building composable, scalable, and effect-safe Scala applications. It introduces domain-specific languages using ADTs and improves them with tagless final encoding for better modularity. It explores free monads and functors to separate computation from execution, and explains ZIO layer for dependency injection, highlighting modularity, testability, and resource safety in functional architectures. Chapter 8: Functional Tools – This chapter introduces essential Scala functional tools for building robust, typesafe, and composable applications. It covers Monocle for immutable data manipulation, Monix for reactive programming, Caliban for type-safe GraphQL, Circe for JSON handling, and ZIO scheduling for concurrency. Additionally, it presents PureConfig for configuration, FS2 for streaming, and Cats collections and retry for functional data structures and retry policies, enabling practical, real-world functional solutions. Chapter 9: Web Implementation in Functional Way – This chapter covers building web applications with functional programming principles like immutability, pure functions, and composability. It highlights functional programming benefits in web development such as easier state management, concurrency, and testability. Key Scala libraries including http4s, Tapir, ZIO HTTP, and sttp are introduced. A to-do app example demonstrates functional HTTP routing and response handling, setting the stage for subsequent functional database integration. Chapter 10: DB Implementation in Functional Way – This chapter covers functional database operations in Scala, emphasizing immutability, pure functions, and side-effect control using monads like IO. It compares four Scala libraries: Slick (type-safe, composable queries), Quill (compile-time query generation), doobie (pure functional raw SQL with Cats Effect), and Skunk (PostgreSQL-focused, highly type-safe). Practical examples include a to-do app with Skunk and guidance on choosing the right library for functional DB access. Chapter 11: Functional Streams for Scala – This chapter explores functional streams in Scala, highlighting their lazy, composable, and resource-efficient handling of large or infinite data sequences. It covers transformations like map, filter, and reduce while maintaining immutability and sideeffect isolation. The chapter introduces FS2 and ZIO streams libraries, comparing their features, concurrency support, and use cases such as real-time analytics and reactive applications, guiding developers to build scalable, efficient data pipelines. Chapter 12: Case Study on Functional Toy Ecommerce Site – This chapter presents a case study on building a toy e-commerce site using functional programming principles and tools. It covers user management, product catalog, cart, checkout, order processing, payments, inventory, reviews, analytics, customer support, and security within a layered architecture. Using Scala, Skunk, and React, the design emphasizes modular, composable services with type-safety, immutability, and effectful computations, illustrating the practical and scalable development of functional applications.