One reason I enjoy the QCon London software development conference is that it reflects programming trends. Organiser Floyd Marinescu described it as by practitioners for practitioners. In previous years I’ve seen themes like disillusionment with enterprise Java, the rise of Agile methodologies, the trend towards dynamic languages, and the benefits of REST.

So what’s hot this year? A couple of trends are striking. One is functional programming. Don Syme, Principal Researcher at Microsoft Research and co-inventor of F#, gave a lively presentation on functional approaches to parallelism and concurrency. He shows screen after screen of equivalent F# and C# code, illustrating how F# is more concise and expressive, as well as being better suited to concurrent development.

F# is one of the languages included by default in Visual Studio 2010, which should be released shortly.

I asked Syme what sort of problems are not well suited to F#. In his reply he described the state of play in Visual Studio 2010, where you can easily create F# libraries but there is no designer support for user interface code, such as Windows Forms or Windows Presentation Foundation. That is merely a tooling issue though.

Syme’s point is that functional programming, and F# in particular, is ideal for today’s programming challenges, including concurrency and asynchronous code.

If nothing else, he convinced me that every .NET programmer should at least be looking at F# and learning what it can do.

The functional programming track at QCon is not just about F#, of course, though in some ways it seems to be the functional language of the moment.

The other theme that has made a big impression is NoSQL, or what the QCon track calls “Non-relational database managers and web-oriented data”.Geir Magnusson from Gilt Groupe talked about the challenge of running a web site which has extreme peaks in traffic, and where every user needs dynamic data and transaction support so simple caching does not work. They were unable to get their relational database store to scale to handle thousands of transactions a second. They solved the problem with an in-memory non-relational database.

In another talk, the BBC discussed their use of CouchDB for highly scalable web sites.