I’ve been working with Microsoft’s new language F# recently and enjoying it. If it catches your interest, you might turn to a book in order to familiarise yourself with the basics. Here are two which I’ve looked at. They are both aimed at experienced developers who are new to F#.

Programming F# by Chris Smith

Programming F# comes from O’Reilly. It kicks off with Hello World and an introduction to the interactive console in Visual Studio 2010 – a great way to try out F#. Next we get a summary of types, and a brief explanation of how to write an F# program – stuff you have to know.

Chapter 3 is an introduction to functional programming, and also mentions type inference, an important F# feature. The following chapter explains mutable programming in F# – yes, you can do it; it is just not the default behaviour – and also covers exceptions. Chapter 5 turns to object-oriented programming in F#, another distinctive feature, while chapter 6 covers aspects specific to .NET such as garbage collection. That’s about half the book, and gets you up and running with the language.

The second half of the book is more interesting, looking at ways of using F#. Smith looks at applied functional programming, including pattern matching, recursion, continuations and closures. Next, there’s a look at applied object orientation. Chapter 9 covers scripting with F# – an interesting use case – and includes welcome examples for things like copying files and automating Microsoft Office. Chapter 10 is a key one, explaining computation expressions that let you create workflows and all-but extend the language. It’s “a very advanced concept that even expert developers can have a hard time grasping,” admits the author, though he presents it clearly.

Next we get a section on a likely reason for picking up F#: asynchronous and parallel programming. There’s a wide-ranging chapter explaining both .NET and F# asynchronous techniques, including the .NET Parallel Extensions. It’s a little confusing, especially since Smith observes that F# asynchronous workflows are sub-optimal for CPU parallelism; he recommends the .NET Parallel Extensions because of the better thread management it offers.

The last chapters cover .NET Reflection, code analysis and generation with Quotations – “deep wizardry”, says the author. An appendix summarises .NET Libraries and F# interop with COM and native code.

While this is an excellent language introduction, and thorough within the topics it covers, some aspects disappointed me. I cannot find any mention of F# agents, based on the MailboxProcessor class (nothing to do with email), which is a surprising omission; F# designer Don Syme sees it as a critical feature for scalable web development. Nor is there anything on graphics processing, another common usage, or any hint about how you might use F# for financial analysis. I also found it rather dry overall – hard to avoid with so much plumbing to cover, but I feel the author could have conveyed a little more excitement about what F# enables. Don’t make this the only F# book you read.

Beginning F# by Robert Pickering

This Apress title covers similar ground as the O’Reilly book, but with a slightly more hands-on and informal style, which on the whole I enjoyed. It starts with an introduction including a quote from Ralf Herbrich at Microsoft Research describing how he converted 1000 lines of C# into 100 lines of F# which performed just as well – this is the kind of real-world touch that makes you want to read on. The second chapter explains how to install F#, including different versions of Visual Studio, the open source SharpDevelop, and Mono on Linux – excellent diversity. Chapter 3 introduces functional programming, in effect a brisk overview of the core of F#. Read it slowly!

The author goes on to look at imperative programming and mutability in F#, and then object orientation, just as Smith did in his book. Chapter 6 is useful overview of how code is organised into modules and namespaces, and also covers comment annotations. Next, Pickering looks at F# libraries, including a brief look at math programming. Chapter 8 covers user interface coding – completely lacking in Smith’s book – complete with a quick look at GTK#, which works on Linux. There’s also a quick look at ASP.NET, Microsoft’s web server platform. Although this little introductions are too brief to be really useful, they do spark ideas about how you might use F#.

Data Access is next, another important real-world topic, covering XML, LINQ (Language Integrated Query) and ADO.NET.

Chapter 10 is when we get to parallel programming and reactive programming – code that waits for an external event before running. Pickering introduces F# agents and the MailboxProcessor class. Next comes a look at distributed applications using sockets, HTTP requests, web services, and Windows Communication Foundation.

Chapter 12 has the intriguing title Language-Oriented Programming, and should be taken together with the next chapter on parsing text. This is where we look at using data structures as little languages, parsing and interpreting text, and extending F# syntax. Finally, chapter 14 is the interop chapter, covering interop with C# as well as platform invocation for COM and native code.

Of the two books, this is the more lively and wide-ranging read, and more likely to enthuse you about the possibilities F# offers, though it skims the surface in places; many topics receive only shallow coverage.

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