The Boo Language

time to read 4 min | 729 words

So, what is this Boo language anyway? I am talking about it fairly often, but I never explained, and I am going to assume that people aren't following links :-)

image Boo is an object oriented, statically typed language for the common language runtime with a Python inspired syntax and focused on language and compiler extensibility.

Boo is an Open Source project, released under the BSD license. This means that you are free to take, modify and use the language and its products in any way you want, without any limitation[1]

. Rodrigo B. de Oliveira started the project, and since then grown in popularity. The project is active and continually evolving. At the time of the writing, the released version of Boo is 0.8.

However, Boo seems to be following the trend of many open source projects, in that that it is not really rushing toward 1.0 release. Boo has been around for a number of years, and I have been using it for production for the last two years.

Production, in this case, means systems that move money around with my neck on the line. I have a high degree of trust in it, obviously.

Beyond being a really malleable language, suitable for DSL. Boo is also a nice language to work with for day-to-day tasks. The SharpDevelop IDE project has support for Boo, so you get the usual benefits. There is an ongoing project to support Boo in Visual Studio, and I have an active interest in seeing support for that being established. I don't much care for which IDE, but I want a standard, checklist driven way of getting a language running.

Here is a secret, I tend to think and write in Boo, translating down to C# because I have to. Boo is a far more flexible language, and the ability to reprogram the compiler makes tedious tasks in other languages an amusing challenge. Those same tedious problems are usually overcome, to some degree, by throwing code generation at the problem until it goes away.image

In Boo, we would usually tell the compiler how we want to handle this, and let the compiler take over from there. This is similar to code generation, except that this is done at the compiler level, which means that we have far more knowledge about what is going on.

For example, let us say that we want to implement the singleton pattern. We need to do quite a bit of work to make it happen. Ensure that creating the singleton is thread safe, lazy initialization, make all the constructors private, ensure that serializable singleton remain singleton through serialization/deserialization, create static Instance property, have no static members on the singleton class.

To do this in most language we would have to follow an implementation pattern and write fairly repetitive code. In Boo, we can capture this usage pattern in an AstAttribute (more on that later) that will do all of that for us, at the cost of a single attribute declaration.

Similar capabilities allow correct usage of disposable, observable, and more advance techniques such as aspect oriented programming.

Some of the capabilities that Boo has can be had using IL Weaving tools such as PostSharp. The problem with those is that using them is something that happens after compilation. As a simple example, you would not be able to create a singleton in this manner, because you would not be able to generate the Instance property at the appropriate time.

Assuming that you want to use the singleton in the same assembly as it was defined, you will not be able to reference the Instance property, it will not exist until the post compile step has run. Boo, however, does this at compile time, so by the time the compiler get to the point where it is resolving the property, it has already been added.

In short, I really like the language and what it allows me to do.

[1] Well, if you are interested in creating a new language called Ba, you probably would want to make it clear where the project ancestry came from…