F# for Fun and Profit

This is the second post in a series on designing software for weavers.

This post is part of the 2025 F# Advent Calendar.

In the first post in this series, we came up with some properties that could be used to test a run-length encoding implementation: The output must contain all the characters from the input, in the same order Two adjacent characters in the output cannot be…

In the previous post we attempted to define some properties for a run-length encoding (RLE) implementation, but got stuck because the random values being generated by FsCheck were not very useful.

In a previous series of posts, I introduced you to the burned-out and lazy programmer known as the Enterprise Developer From Hell, or the EDFH for short.

This series of posts is a follow-up to my previous series on property-based testing and the Enterprise Developer From Hell.

These terms and conditions form your agreement with this site (hereafter, the SITE) and ScottW (hereafter, ME).

In this series, we looked at six different approaches to dependency injection.

In this series, we are looking at six different approaches to dependency injection.

In this series, we are looking at six different approaches to dependency injection.

In this series, we are looking at six different approaches to dependency injection.

This post is part of the 2020 F# Advent Calendar.

In this series, we’ll look at how so-called “applicative parsers” work.

In this series of posts, I’ll attempt to describe some of the core functions for dealing with generic data types (such as Option and List).

This series of posts will give you a guided tour through the main features of F# and then show you ways that F# can help you in your day-to-day development.

In this series, we’ll look at a very common “pattern” known as a monoid.

F# is not just about functions; the powerful type system is another key ingredient.

This series of posts will introduce you to the fundamentals of functional programming – what does it really mean to “program functionally”, and how this approach differs from object oriented or imperative programming.

“I think I understand functional programming at the micro level, and I have written toy programs, but how do I actually go about writing a complete application, with real data, real error handling, and so on?"

This series of posts will introduce you to the fundamentals of property-based testing: how it is different from traditional example-based testing, why it is important, and how to work with properties in theory and practice.

Do you want to port C# code to F#?

This is a placeholder for a series I haven’t written yet.

As has been stressed many times before, F# is fundamentally a functional language at heart, yet the OO features have been nicely integrated and do not have a “tacked-on” feeling.

In this series of posts, I’ll look at how you can thread state through a series of pure functions in a convenient way.

In this series of posts, I’ll look at how you might handle the common security challenge of authorization.

In this series of posts we’ll look at how functions and values are combined into expressions, and the different kinds of expressions that are available in F#.

In this series, we’ll look at some of the ways we can use types as part of the design process.

One of the most common complaints about F# is that it requires code to be in dependency order.

In this series, you’ll learn what computation expressions are, some common patterns, and how to make your own.

One comment I hear often is a complaint about the gap between theory and practice in F# and functional programming in general.

In this series, we’ll look at recursive types and how to use them, and on the way, we’ll look at catamorphisms, tail recursion, the difference between left and right folds, and more.

So you’re all excited about functional programming, and you’ve been learning F# in your spare time, and you’re annoying your co-workers by ranting about how great it is, and you’re itching to use it for serious stuff at work… But then you hit a brick wall.

This post is part of the 2019 F# Advent Calendar.

This post is part of the 2018 F# Advent Calendar.

This post is part of the F# Advent Calendar in English 2017 project.

This post is part of the F# Advent Calendar in English 2016 project.

Last year, I wrote a post called “Happy F# Day”, explaining why I thought F# needed a “birthday” that we could celebrate as a community.

UPDATE: Slides and video from my talk on this topic In this, the third part of my two-part mega-post, I’m continuing to stretch the simple turtle graphics model to the breaking point.

UPDATE: Slides and video from my talk on this topic This post is part of the F# Advent Calendar in English 2015 project.

UPDATE: Slides and video from my talk on this topic This post is part of the F# Advent Calendar in English 2015 project.

UPDATE: Slides and video from my talk on this topic In this series, we are looking at how applicative parsers and parser combinators work.

UPDATE: Slides and video from my talk on this topic In this series, we are looking at how applicative parsers and parser combinators work.

UPDATE: Slides and video from my talk on this topic In this series, we are looking at how applicative parsers and parser combinators work.

UPDATE: Slides and video from my talk on this topic In this series, we’ll look at how so-called “applicative parsers” work.

This post is the sixth in a series.

This post is the fifth in a series.

This post is the fourth in a series.

This post is the third in a series.

This post is the second in a series.

In this series, we’ll look at recursive types and how to use them, and on the way, we’ll look at catamorphisms, tail recursion, the difference between left and right folds, and more.