Programming, Software and Code

Already this advent series of posts is an unmitigated disaster. The last two days of ommissions can be squarely blamed on my wife and her parents, and last night I will blame on Septa (for eating 5 hours of my day because of “mechanical problems”). Here, finally, is day 3 of my miserable failure of an advent calendar.

For the third post in my almost-advent calendar, I’m going to talk about Winxed.

Winxed, written by long-time Parrot hacker NotFound, is quite an interesting project and is definitely worth learning more about. It serves as something of a counterpoint to NQP, the other lower-level Parrot language in the ecosystem but the two aren’t competing. I think they are very complimentary. Where NQP is designed to help building compilers (Rakudo Perl6 especially), Winxed seems much more geared towards writing libraries and utilities. It’s for this reason that I’ve written my library project, Rosella, in Winxed.

In return for making such an awesome language, I’ve turned around and started writing some comprehensive documentation about Winxed on the Rosella website.

Winxed is written in itself using a home-brewed recursive descent parser. To perform the bootstrapping, the stage 0 winxed compiler is written in C++. In stage 0, a paired-down version of the language is used to compile the stage 1 compiler which is written in that subset. Stage 1 is used to compile stage 2, which is a more full-featured version of the language. Stage 2 is used to compile itself into stage 3. Stage 3 is what you and I use when we install Winxed.

It sounds much more complicated than it is, but the net result is clear and simple: Winxed written in Winxed. If you know Winxed, or are familiar with some of the big languages it is inspired by (C++, Java, C#, JavaScript), you’ll be able to not only write software for Parrot, but also be able to hack on the Winxed compiler itself. I’ve submitted a few patches and feature additions, and I’ve found it to be a pleasure to work on.

It’s not anything goes on the compiler, however. NotFound maintains pretty tight editorial control over the software. The consistency of vision and planning does produce refreshingly nice results, though. He’s very good about taking requests and suggestions, so if you see something that’s missing definitely drop him a line.

Since bundling with Parrot in th 3.6.0 release, which incidentally is when NotFound started keeping track of version numbers, the language has come a long way: Various optimizations, a debugging mode with optional asserts and conditionals, several new built-in functions, support for multiple dispatch and most recently a new “inline” feature which allows you to inline certain types of code for performance improvements by avoiding extra PCC calls.

Here is a random-ish sample of Winxed code that I’ve been playing around with recently, written in Winxed for testing some new ideas I’m thinking of adding to Rosella:

function main[main](var args)
{
    var rand = Rosella.Random.default_uniform_random();
    var mutator = new Rosella.Genetic.Mutator(
        function() {
            float value = float(rand.get_float()) * 1000.0;
            return new Data(value);
        }
    );
    var e = new Rosella.Genetic.Engine([10, 3, 0], mutator,
        function(var d) {
            int x = int(d.value) - 200;
            ${ abs x };
            return x;
        }
    );
    var w = e.run(500).first().data();
    say(float(w.value));
}

This sample is a driver program for a new Genetic Algorithms library that I’m playing with. This toy example uses the Genetic Engine type to pick some random numbers at each generation for five hundred generations to try and get a random number which is closest to 200.0. It’s a trivial example to be sure, and I’ll write more about that library in the future if anything ever comes of it. That’s not the important part of this example, however. The important part is the Winxed syntax. The syntax should be immediately familiar to anybody who has used JavaScript or C++ and any of its descendents. Here we can clearly see closures created with the function keyword, creating objects with new (Winxed is OO, not prototype-based like JavaScript), low-level types like float and int, Parrot Sub flags like [main] (AKA :main in PIR) and calling PIR opcodes directly (the ${ ... } syntax). Winxed in a nutshell is an an answer to this question: What would it look like if I took a language like C++ or JavaScript and bent it to work closely with Parrot?

Winxed creates a nice mix of dynamic behavior with static analysis. There is plenty of syntax and semantics in the compiler that can be used to inline code, propagate constants, statically link functions by name instead of doing named lookups, checking known types at compile time and issuing warnings, and other tools that would be more familiar to a user of statically typed languages.

I don’t know where NotFound is planning to take Winxed in 2012. His relentless pursuit of new features, better internals, more optimizations, better diagnostics and other improvements leaves open many potential avenues for him to travel down.

I have a few ideas for features I might like to propose and provide patches, many of which will be intended to mirror changes that will need to be made in Parrot. I have been thinking about submitting a patch to add some cleaner syntax for parameter and argument flags instead of using PIR flags by name directly. I’m also keen to get Winxed updated to use some of my new PCC changes as soon as they are available. It will make both a great test case for the new functionality and a good demonstration of any performance benefits to be had. Eventually I would like to get Winxed updated to generate .pbc packfiles directly instead of generating PIR and using IMCC as an intermediary. That’s a pretty big project, and might have to wait until we get more work done on PACT. Again, this would make an excellent demonstration of the functionality, when we have it ready to test.

I personally use Winxed to implement my Rosella project and the first stage of my JavaScript compiler “Jaesop”. Other people are using it as well. Hacker plobsing has used it for a few projects, including an OMeta parser port. Hacker benabik is using it for PACT, a re-design of the Parrot Compiler Toolkit. Dukeleto is writing bindings for libgit2 in Winxed. NotFound is writing xlib bindings in Winxed called Guitor (and some of the example programs are actually quite impressive already). There are many other examples of projects that are or will be written in Winxed, and I’m sure the number will only increase in 2012.

If you’re doing systems-level library or utility work on Parrot in 2012, Winxed is probably the language you are going to be using. I’ll talk about compilers and NQP in later posts.