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 Monday, March 22, 2010
How to (and not to) give a talk on F#

Michael Easter called me out over Twitter tonight, entirely fairly. This blog post is to attempt to make right.

Context: Tonight was a .NET Developer Association meeting in Redmond, during which we had two presentations: one on Entity Framework, and one on F#. The talk on F#, while well-meaning and delivered by somebody I've not yet met personally, suffered from several failures that I believe to be endemic to Microsoft's approach to presenting F#. I don't fault the speaker—I think Michael was set up to fail from the very beginning. Thus, I decided that it was time for me to "put up" and describe the structural failures I've seen in several talks attempting to describe F# to the general .NET computing community. (I think these could probably be generalized to presenting a new language to any general computing community, but I'll keep it focused on F# for now.)

In no particular order:

  • DON'T use a demo based on a mathematical principle (like Fibonacci, factorial, or some other exponent-hugging formula). I ask you, how many developers find themselves writing that kind of code on a daily basis? If you offer up purely mathematical examples, you will create the impression that F# is only good for high-scale numerical and mathematical computing, such as what scientists use, and you will essentially convince everybody in the room that F# belongs in that class of programming language that doesn't have anything to do with them.
  • DO use a demo based on real-world environments or problems. Use domain types that could have come from a regular line-of-business scenario; my favorite is "Person", since that can serve as a base type for other, more domain-specific, types (like "Student", "Instructor", "Employee", and whatever).
  • DON'T stress the F# Interactive environment. Yes, it's great that F# has an interactive environment and a REPL. But accept that this is not what the general development community cares about, or even sees value in. In fact, the more you stress the REPL/interactive window in F#, the more likely you are to get a question at the end of the talk asking you to compare F# to Python or Perl. Then you end up having to argue the benefits of static typing and type inference over dynamic/duck typing, which really makes no sense in a scripting tool, which is only on the questioners' mind because you put it there by stressing the REPL.
  • DO show F# code being called by other assemblies, and vice versa. At the end of the day, the watchword here should be "interoperability", because no matter how eloquent your presentation, you're not going to get the audience to suddenly abandon their C# and Visual Basic and switch over to writing everything in F#, because there's just too many scenarios where F# is not the right answer (UI "top of the stack" kinds of things being at the top of my "not great for F#" list). Stress how an F# type is just a class, with methods that can be invoked from C# and vice versa.
  • DON'T answer the inevitable "why should I care?" question with the word "productivity". I hate to be the one to point this out, but every language ever introduced has held this up as a reason to switch to it, and none of them have ever really felt like they were a productivity boost, at least not in the long run. And if you answer with, "Because I just think that way", that's a FAIL on your part, because I can't see how your thinking changes mine. (You may also like the Pittsburgh Steelers, while I know they can't hold a candle to the New Orleans Saints—now where are we?)
  • DO answer the inevitable "why should I care?" question with tangible real-world scenarios or examples. Give two or three cases, abstract or concrete, where F# makes the developers' life easier, and how. And frankly, I would sprinkle in a few cases where F# isn't a net win, because everybody knows, deep down, that no one language is perfect for all scenarios. (Only marketing and sales people seem to think there is.)
  • DON'T jump straight into all this functional jazz. I hate to tell you this, but most of the developer community is not convinced that functional programming is "obviously" the right way to program. Attempting to take them deep into functional mojo is only going to lose them and overwhelm them and quite likely convince them that functional programming is for math majors. Use of the terms "catamorphism" or "monad" or "partial application" or "currying" in your introductory talk is an exercise in stroking your own ego, not in teaching the audience something useful.
  • DO stress that F# can do everything C# or Visual Basic can do. Developers like to start with the familiar—it's why every programming language starts with the "Hello World" example, not only because it's simple and straightforward but because developers have come to expect it. F# can build types just like C# can, so do that, and use that as a framework from which to build up their understanding of the syntax and semantics.
  • DON'T assume you can give an introduction to a programming language in 20 minutes. I don't care how good you are as a presenter, it can't be done. 50 minutes would be pushing it. 90 minutes is maybe just enough to get through enough syntax to get the audience to the point where they can read a commonplace F# program. Maybe.
  • DO tease the hell out of them for 20 minutes. If you only have 20 minutes, then create a super-sexy demo (not a math-based or scripting-based one), show them the demo, then point out that this is written in 35 lines of F#, and if they want to understand what's going on in that 35 lines, here's some resources to go learn F#. Leave them wanting more.

Again, I'm not faulting Michael (tonight's speaker): I think he bravely attempted what was likely to be a failure regardless of who was giving the talk. My hope is that as others start to step up to talk about F# to their coworkers and fellow user group members, this will help avoid a few more "Oh, so F# is totally irrelevant to me" reactions.