PureScript by Example

Functional Programming for the Web

Learn functional programming for the web by solving practical problems using the PureScript programming language. "PureScript By Example" will motivate functional programming techniques like maps, folds, type classes and monads by applying them to real-world problems such as form validation, AJAX callbacks and drawing with the canvas. 100% of the author royalties on purchases of this book are donated to Code Club, a nationwide network of volunteer-led after school coding clubs.

Phil Freeman

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About

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

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About the Author

Phil Freeman

I am a developer living in Los Angeles, CA. I work principally in Scala, Haskell and TypeScript.

I am the original developer of the PureScript programming language and compiler, and I am currently working on the PureScript by Example book.

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Spanish

Table of Contents

1.Introduction

1.1Functional JavaScript
1.2Types and Type Inference
1.3Polyglot Web Programming
1.4Prerequisites
1.5About You
1.6How to Read This Book
1.7Getting Help
1.8About the Author
1.9Acknowledgements

2.Getting Started

2.1Chapter Goals
2.2Introduction
2.3Installing PureScript
2.4Installing Tools
2.5Hello, PureScript!
2.6Compiling for the Browser
2.7Removing Unused Code
2.8Compiling CommonJS Modules
2.9Tracking Dependencies with Bower
2.10Computing Diagonals
2.11Testing Code Using the Interactive Mode
Exercises
2.12Conclusion

3.Functions and Records

3.1Chapter Goals
3.2Project Setup
3.3Simple Types
3.4Quantified Types
3.5Notes On Indentation
3.6Defining Our Types
3.7Type Constructors and Kinds
3.8Displaying Address Book Entries
3.9Test Early, Test Often
3.10Creating Address Books
3.11Curried Functions
3.12Querying the Address Book
3.13Infix Function Application
3.14Function Composition
3.15Tests, Tests, Tests …
Exercises
3.16Conclusion

4.Recursion, Maps And Folds

4.1Chapter Goals
4.2Project Setup
4.3Introduction
4.4Recursion on Arrays
Exercises
4.5Maps
4.6Infix Operators
4.7Filtering Arrays
Exercises
4.8Flattening Arrays
4.9Array Comprehensions
4.10Do Notation
4.11Guards
Exercises
4.12Folds
4.13Tail Recursion
4.14Accumulators
4.15Prefer Folds to Explicit Recursion
Exercises
4.16A Virtual Filesystem
4.17Listing All Files
Exercises
4.18Conclusion

5.Pattern Matching

5.1Chapter Goals
5.2Project Setup
5.3Simple Pattern Matching
5.4Simple Patterns
5.5Guards
Exercises
5.6Array Patterns
5.7Record Patterns and Row Polymorphism
5.8Nested Patterns
5.9Named Patterns
Exercises
5.10Case Expressions
5.11Pattern Match Failures and Partial Functions
5.12Algebraic Data Types
5.13Using ADTs
5.14Record Puns
Exercises
5.15Newtypes
5.16A Library for Vector Graphics
5.17Computing Bounding Rectangles
Exercises
5.18Conclusion

6.Type Classes

6.1Chapter Goals
6.2Project Setup
6.3Show Me!
Exercises
6.4Common Type Classes
Exercises
6.5Type Annotations
6.6Overlapping Instances
6.7Instance Dependencies
Exercises
6.8Multi Parameter Type Classes
6.9Functional Dependencies
6.10Nullary Type Classes
6.11Superclasses
Exercises
6.12A Type Class for Hashes
Exercises
6.13Conclusion

7.Applicative Validation

7.1Chapter Goals
7.2Project Setup
7.3Generalizing Function Application
7.4Lifting Arbitrary Functions
7.5The Applicative Type Class
7.6Intuition for Applicative
7.7More Effects
7.8Combining Effects
Exercises
7.9Applicative Validation
7.10Regular Expression Validators
Exercises
7.11Traversable Functors
Exercises
7.12Applicative Functors for Parallelism
7.13Conclusion

8.The Eff Monad

8.1Chapter Goals
8.2Project Setup
8.3Monads and Do Notation
8.4The Monad Type Class
8.5Monad Laws
8.6Folding With Monads
8.7Monads and Applicatives
Exercises
8.8Native Effects
8.9Side-Effects and Purity
8.10The Eff Monad
8.11Extensible Effects
8.12Interleaving Effects
8.13The Kind of Eff
8.14Records And Rows
8.15Fine-Grained Effects
8.16Handlers and Actions
8.17Mutable State
Exercises
8.18DOM Effects
8.19An Address Book User Interface
Exercises
8.20Conclusion

9.Canvas Graphics

9.1Chapter Goals
9.2Project Setup
9.3Simple Shapes
9.4Putting Row Polymorphism to Work
Exercises
9.5Drawing Random Circles
9.6Transformations
9.7Preserving the Context
9.8Global Mutable State
Examples
9.9L-Systems
Exercises
9.10Conclusion

10.The Foreign Function Interface

10.1Chapter Goals
10.2Project Setup
10.3A Disclaimer
10.4Calling PureScript from JavaScript
10.5Understanding Name Generation
10.6Runtime Data Representation
10.7Representing ADTs
10.8Representing Quantified Types
10.9Representing Constrained Types
Exercises
10.10Using JavaScript Code From PureScript
10.11Wrapping JavaScript Values
10.12Defining Foreign Types
10.13Functions of Multiple Arguments
10.14Representing Side Effects
10.15Defining New Effects
Exercises
10.16Working With Untyped Data
10.17Handling Null and Undefined Values
10.18Generic JSON Serialization
Exercises
10.19Conclusion

11.Monadic Adventures

11.1Chapter Goals
11.2Project Setup
11.3How To Play The Game
11.4The State Monad
Exercises
11.5The Reader Monad
Exercises
11.6The Writer Monad
Exercises
11.7Monad Transformers
11.8The ExceptT Monad Transformer
11.9Monad Transformer Stacks
Exercises
11.10Type Classes to the Rescue!
11.11Alternatives
11.12Monad Comprehensions
11.13Backtracking
Exercises
11.14The RWS Monad
11.15Implementing Game Logic
11.16Running the Computation
Exercises
11.17Handling Command Line Options
Exercises
11.18Conclusion

12.Callback Hell

12.1Chapter Goals
12.2Project Setup
12.3The Problem
12.4The Continuation Monad
Exercises
12.5Putting ExceptT To Work
Exercises
12.6A HTTP Client
Exercises
12.7Parallel Computations
Exercises
12.8Conclusion

13.Generative Testing

13.1Chapter Goals
13.2Project Setup
13.3Writing Properties
13.4Improving Error Messages
Exercises
13.5Testing Polymorphic Code
Exercises
13.6Generating Arbitrary Data
Exercises
13.7Testing Higher-Order Functions
13.8Writing Coarbitrary Instances
13.9Testing Without Side-Effects
Exercises
13.10Conclusion

14.Domain-Specific Languages

14.1Chapter Goals
14.2Project Setup
14.3A HTML Data Type
14.4Smart Constructors
Exercises
14.5Phantom Types
Exercises
14.6The Free Monad
14.7Interpreting the Monad
Exercises
14.8Extending the Language
Exercises
14.9Conclusion

Causes

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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