Contents of the book

A directory of useful pages

Getting started

• Installing and using F# will get you started.

• Why use F#? An interactive tour of F#.

• Learning F# has tips to help you learn more effectively.

• Troubleshooting F# for when you have problems getting your code to compile.

and then you can try...

• Twenty six low-risk ways to use F# at work. You can start right now -- no permission needed!

Tutorials

The following series are tutorials on the key concepts of F#.

• Thinking functionally starts from basics and explains how and why functions work the way they do.

• Expressions and syntax covers the common expressions such as pattern matching, and has a post on indentation.

• Understanding F# types explains how to define and use the various types, including tuples, records, unions, and options.

• Designing with types explains how to use types as part of the design process, making illegal states unrepresentable.

• Choosing between collection functions. If you are coming to F# from C#, the large number of list functions can be overwhelming, so I have written this post to help guide you to the one you want.

• Property-based testing: the lazy programmer's guide to writing 1000's of tests.

• Understanding computation expressions demystifies them and shows how you can create your own.

Functional patterns

These posts explain some core patterns in functional programming -- concepts such as "map", "bind", monads and more.

• Railway Oriented Programming: A functional approach to error handling
• State Monad: An introduction to handling state using the tale of Dr Frankenfunctor and the Monadster.
• Reader Monad: Reinventing the Reader monad.
• Map, bind, apply, lift, sequence and traverse: A series describing some of the core functions for dealing with generic data types.
• Monoids without tears: A mostly mathless discussion of a common functional pattern.
• Fold and recursive types: A look at recursive types, catamorphisms, tail recursion, the difference between left and right folds, and more.
• Understanding Parser Combinators: Creating a parser combinator library from scratch.
• Thirteen ways of looking at a turtle: demonstrates many different techniques for implementing a turtle graphics API, including state monads, agents, interpreters, and more!

Worked examples

These posts provide detailed worked examples with lots of code!

• Designing for correctness: How to make illegal states unrepresentable (a shopping cart example).
• Stack based calculator: Using a simple stack to demonstrate the power of combinators.
• Parsing commmand lines: Using pattern matching in conjunction with custom types.
• Roman numerals: Another pattern matching example.
• Calculator Walkthrough: The type-first approach to designing a Calculator.
• Enterprise Tic-Tac-Toe: A walkthrough of the design decisions in a purely functional implementation
• Writing a JSON Parser.

Specific topics in F# ##

General:

• Four key concepts that differentiate F# from a standard imperative language.
• Understanding F# indentation.
• The downsides of using methods.

Functions:

• Currying.
• Partial Application.

Control Flow:

• Match..with expressions and creating folds to hide the matching.
• If-then-else and loops.
• Exceptions.

Types:

• Option Types especially on why None is not the same as null.
• Record Types.
• Tuple Types.
• Discriminated Unions.
• Algebraic type sizes and domain modelling.

Controversial posts

• Is your programming language unreasonable? or, why predictability is important.
• Commentary on 'Roman Numerals Kata with Commentary'. My approach to the Roman Numerals Kata.
• Ten reasons not to use a statically typed functional programming language. A rant against something I don't get.
• We don't need no stinking UML diagrams or, why in many cases, using UML for class diagrams is not necessary.