Tao Liu - F# for C# Developers

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People often ask, What can F# do that C# cannot? In this book, you will discover much of what F# can do! You will see familiar things such as object programming and design patterns. Further, you will also see powerful new things like pattern matching, piping, first-class events, object expressions, options, tuples, records, discriminated unions, active patterns, agents, computation expressions and, perhaps most distinctively, type providers.

However, we also need to ask the other question: What can C# do that F# cannot? There is one important part to this answer that I will focus on here: C# can cause NullReferenceExceptions . What? I hear you ask. Does F# not have nulls? Right! Perhaps the most important thing the C# programmer needs to know about F# is that F# does not use nulls in routine programming.

Lets look at some evidence. People using F# at a major UK energy company did a study of two similar ETL (Extract, Transform, Load) applications.[] Broadly speaking, the applications were in the same zone in terms of functionality or, if anything, the F# application implemented more features. The F# project had a very low bug rate, and its code was 26 times smaller. The size difference is not only the result of language differences; there are also differences in design methodology. The C# project is characterized by the inappropriate overuse of elaborate object abstractions often seen in Java projectsfor example, elaborate and unnecessary class hierarchies.

Interestingly, the comparison records that the C# project had 3036 explicit null checks, where a functionally similar F# project had 27, a reduction of 112 times in the total number of null checks. The other statistics in the comparison shown are also compelling, particularly the defects since go live: the F# code had zero defects since go live, and the C# code had too many. These are not unrelated: nulls cause defects. In my opinion, the lack of nulls in routine coding alone makes it worth switching your programming teams to F# where possible.

In this book, you will learn many wonderful things about F#. But dont lose sight of the big picture: F# is about writing accurate, correct, efficient, interoperable code that gets deployed on time in enterprise scenarios. It does this partly by removing the most pernicious of evils: nulls. If you and your team embrace it, then, all else being equal, your life will be simpler, happy, and more productive.

Don Syme

F# Community Contributor

F# is a functional programming language from Microsoft. It is the first class language shipped in Visual Studio. It has been applied successfully in several areas, such as in the areas of financial software and web development. If you are a C# developer and want to use functional programming to write concise code with fewer bugs, F# is the right tool for you.

F# for C# Developers introduces, in an organized way, the F# language and several applications. It starts from how F# can perform imperative and object-oriented programming tasks and then moves on to covering unique F# features, such as type providers. By introducing F# design patterns with a large number of samples, this book not only delivers a basic introduction but also helps you apply F# in your daily programming work.

In addition to covering core F# core features, I also discuss F# HTML5 development, F# Azure development, and using general-purpose graphics processing units (GPGPUs) with F#. Beyond the explanatory content, each chapter includes examples and downloadable sample projects you can explore for yourself.