About 6 years ago, I started writing the DSLs in Boo book, it came out in 2010, and today I got an email saying that this is now officially out of print. It was never a hugely popular book, so I’m not really surprised, but it really got me thinking.
I got to build several DSLs for production during the time I was writing this book, but afterward, I pretty much pivoted hard to RavenDB, and didn’t do much with DSLs since. However, the knowledge acquired during the writing of this book has actually been quite helpful when writing RavenDB itself.
I’m not talking about the design aspects of writing a DSLs, or the business decisions that are involved with that, although that is certainly a factor. I’m talking about the actual technical details of working with a language, a parser, etc.
In fact, you won’t see that, probably, but RavenDB indexes and transformers are actually DSLs, and they use a lot of the techniques that I talk about in the book. We start with something that looks like a C# code, but what ends up running is actually something that is far different. The Linq provider, too, rely heavily on those same techniques. We show you one thing but actually do something quite different under the cover.
It is interesting to see how the actual design of RavenDB was influenced by what my own history and the choices I made in various places. If I wasn’t well versed with abusing a language, I would probably have to go with something like CouchDB’s views, for example.