PureScript by Example
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PureScript by Example

Functional Programming for the Web

About the Book

PureScript is a small strongly, statically typed programming language with expressive types, written in and inspired by Haskell, and compiling to Javascript. 

Functional programming in JavaScript has seen quite a lot of popularity recently, but large-scale application development is hindered by the lack of a disciplined environment in which to write code. PureScript aims to solve that problem by bringing the power of strongly-typed functional programming to the world of JavaScript development.

This book will show you how to get started with the PureScript programming language, from the basics (setting up a development environment) to the advanced.

Each chapter will be motivated by a particular problem, and in the course of solving that problem, new functional programming tools and techniques will be introduced. Here are some examples of problems that will be solved in this book:

  • Transforming data structures with maps and folds
  • Form field validation using applicative functors
  • Testing code with QuickCheck
  • Using the canvas
  • Domain specific language implementation
  • Working with the DOM
  • JavaScript interoperability
  • Dealing with callback hell

Translations

About the Author

Phil Freeman
Phil Freeman

I am a developer living in Los Angeles, CA. I work principally in Scala, Haskell and TypeScript. I love using functional techniques to solve real world problems.

I am the original developer of the PureScript programming language and compiler, and have written several of its core libraries.

Table of Contents

  • 1. Introduction
    • 1.1 Functional JavaScript
    • 1.2 Types and Type Inference
    • 1.3 Polyglot Web Programming
    • 1.4 Prerequisites
    • 1.5 About You
    • 1.6 How to Read This Book
    • 1.7 Getting Help
    • 1.8 About the Author
    • 1.9 Acknowledgements
  • 2. Getting Started
    • 2.1 Chapter Goals
    • 2.2 Introduction
    • 2.3 Installing PureScript
    • 2.4 Installing Tools
    • 2.5 Hello, PureScript!
    • 2.6 Compiling for the Browser
    • 2.7 Removing Unused Code
    • 2.8 Compiling CommonJS Modules
    • 2.9 Tracking Dependencies with Bower
    • 2.10 Computing Diagonals
    • 2.11 Testing Code Using the Interactive Mode
    • 2.12 Conclusion
  • 3. Functions and Records
    • 3.1 Chapter Goals
    • 3.2 Project Setup
    • 3.3 Simple Types
    • 3.4 Quantified Types
    • 3.5 Notes On Indentation
    • 3.6 Defining Our Types
    • 3.7 Type Constructors and Kinds
    • 3.8 Displaying Address Book Entries
    • 3.9 Test Early, Test Often
    • 3.10 Creating Address Books
    • 3.11 Curried Functions
    • 3.12 Querying the Address Book
    • 3.13 Infix Function Application
    • 3.14 Function Composition
    • 3.15 Tests, Tests, Tests …
    • 3.16 Conclusion
  • 4. Recursion, Maps And Folds
    • 4.1 Chapter Goals
    • 4.2 Project Setup
    • 4.3 Introduction
    • 4.4 Recursion on Arrays
    • 4.5 Maps
    • 4.6 Infix Operators
    • 4.7 Filtering Arrays
    • 4.8 Flattening Arrays
    • 4.9 Array Comprehensions
    • 4.10 Do Notation
    • 4.11 Guards
    • 4.12 Folds
    • 4.13 Tail Recursion
    • 4.14 Accumulators
    • 4.15 Prefer Folds to Explicit Recursion
    • 4.16 A Virtual Filesystem
    • 4.17 Listing All Files
    • 4.18 Conclusion
  • 5. Pattern Matching
    • 5.1 Chapter Goals
    • 5.2 Project Setup
    • 5.3 Simple Pattern Matching
    • 5.4 Simple Patterns
    • 5.5 Guards
    • 5.6 Array Patterns
    • 5.7 Record Patterns and Row Polymorphism
    • 5.8 Nested Patterns
    • 5.9 Named Patterns
    • 5.10 Case Expressions
    • 5.11 Pattern Match Failures and Partial Functions
    • 5.12 Algebraic Data Types
    • 5.13 Using ADTs
    • 5.14 Record Puns
    • 5.15 Newtypes
    • 5.16 A Library for Vector Graphics
    • 5.17 Computing Bounding Rectangles
    • 5.18 Conclusion
  • 6. Type Classes
    • 6.1 Chapter Goals
    • 6.2 Project Setup
    • 6.3 Show Me!
    • 6.4 Common Type Classes
    • 6.5 Type Annotations
    • 6.6 Overlapping Instances
    • 6.7 Instance Dependencies
    • 6.8 Multi Parameter Type Classes
    • 6.9 Functional Dependencies
    • 6.10 Nullary Type Classes
    • 6.11 Superclasses
    • 6.12 A Type Class for Hashes
    • 6.13 Conclusion
  • 7. Applicative Validation
    • 7.1 Chapter Goals
    • 7.2 Project Setup
    • 7.3 Generalizing Function Application
    • 7.4 Lifting Arbitrary Functions
    • 7.5 The Applicative Type Class
    • 7.6 Intuition for Applicative
    • 7.7 More Effects
    • 7.8 Combining Effects
    • 7.9 Applicative Validation
    • 7.10 Regular Expression Validators
    • 7.11 Traversable Functors
    • 7.12 Applicative Functors for Parallelism
    • 7.13 Conclusion
  • 8. The Eff Monad
    • 8.1 Chapter Goals
    • 8.2 Project Setup
    • 8.3 Monads and Do Notation
    • 8.4 The Monad Type Class
    • 8.5 Monad Laws
    • 8.6 Folding With Monads
    • 8.7 Monads and Applicatives
    • 8.8 Native Effects
    • 8.9 Side-Effects and Purity
    • 8.10 The Eff Monad
    • 8.11 Extensible Effects
    • 8.12 Interleaving Effects
    • 8.13 The Kind of Eff
    • 8.14 Records And Rows
    • 8.15 Fine-Grained Effects
    • 8.16 Handlers and Actions
    • 8.17 Mutable State
    • 8.18 DOM Effects
    • 8.19 An Address Book User Interface
    • 8.20 Conclusion
  • 9. Canvas Graphics
    • 9.1 Chapter Goals
    • 9.2 Project Setup
    • 9.3 Simple Shapes
    • 9.4 Putting Row Polymorphism to Work
    • 9.5 Drawing Random Circles
    • 9.6 Transformations
    • 9.7 Preserving the Context
    • 9.8 Global Mutable State
    • 9.9 L-Systems
    • 9.10 Conclusion
  • 10. The Foreign Function Interface
    • 10.1 Chapter Goals
    • 10.2 Project Setup
    • 10.3 A Disclaimer
    • 10.4 Calling PureScript from JavaScript
    • 10.5 Understanding Name Generation
    • 10.6 Runtime Data Representation
    • 10.7 Representing ADTs
    • 10.8 Representing Quantified Types
    • 10.9 Representing Constrained Types
    • 10.10 Using JavaScript Code From PureScript
    • 10.11 Wrapping JavaScript Values
    • 10.12 Defining Foreign Types
    • 10.13 Functions of Multiple Arguments
    • 10.14 Representing Side Effects
    • 10.15 Defining New Effects
    • 10.16 Working With Untyped Data
    • 10.17 Handling Null and Undefined Values
    • 10.18 Generic JSON Serialization
    • 10.19 Conclusion
  • 11. Monadic Adventures
    • 11.1 Chapter Goals
    • 11.2 Project Setup
    • 11.3 How To Play The Game
    • 11.4 The State Monad
    • 11.5 The Reader Monad
    • 11.6 The Writer Monad
    • 11.7 Monad Transformers
    • 11.8 The ExceptT Monad Transformer
    • 11.9 Monad Transformer Stacks
    • 11.10 Type Classes to the Rescue!
    • 11.11 Alternatives
    • 11.12 Monad Comprehensions
    • 11.13 Backtracking
    • 11.14 The RWS Monad
    • 11.15 Implementing Game Logic
    • 11.16 Running the Computation
    • 11.17 Handling Command Line Options
    • 11.18 Conclusion
  • 12. Callback Hell
    • 12.1 Chapter Goals
    • 12.2 Project Setup
    • 12.3 The Problem
    • 12.4 The Continuation Monad
    • 12.5 Putting ExceptT To Work
    • 12.6 A HTTP Client
    • 12.7 Parallel Computations
    • 12.8 Conclusion
  • 13. Generative Testing
    • 13.1 Chapter Goals
    • 13.2 Project Setup
    • 13.3 Writing Properties
    • 13.4 Improving Error Messages
    • 13.5 Testing Polymorphic Code
    • 13.6 Generating Arbitrary Data
    • 13.7 Testing Higher-Order Functions
    • 13.8 Writing Coarbitrary Instances
    • 13.9 Testing Without Side-Effects
    • 13.10 Conclusion
  • 14. Domain-Specific Languages
    • 14.1 Chapter Goals
    • 14.2 Project Setup
    • 14.3 A HTML Data Type
    • 14.4 Smart Constructors
    • 14.5 Phantom Types
    • 14.6 The Free Monad
    • 14.7 Interpreting the Monad
    • 14.8 Extending the Language
    • 14.9 Conclusion

Causes Supported

Code Club

https://www.codeclub.org.uk

A nationwide network of volunteer-led after school coding clubs for children aged 9-11.

We create projects for our volunteers to teach at after school coding clubs or at non-school venues such as libraries. The projects we make teach children how to program by showing them how to make computer games, animations and websites. Our volunteers go to their local club for an hour a week and teach one project a week. Each term the students will progress and learn more whilst at the same time using their imaginations and making creative projects. Terms 1 & 2 use Scratch to teach the basics of programming. Term 3 teaches the basics of web development using HTML and CSS. Term 4 teaches Python and so on. We’d like to put a Code Club in every single primary school in the country. There are over 21,000 primary schools in the UK, it’s a big task but we think we can do it!

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