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Status of perl6 on Parrot, 2007-12-04
This is an update on the status of Perl 6 on Parrot development as of December 4, 2007.
Progress in November 2007
The last report was published in November as a "road map" for continued development of the Perl 6 on Parrot compiler (perl6). Since then we've basically been following the steps outlined on the road map and we are seeing significant progress on the compiler.
The big news for this month is that we are now using a lightweight Perl 6 translator ("NQP") to implement the translation components of the perl6 compiler. Making this transition means we are currently failing quite a few tests in the test suite, but Jerry Gay and I are rapidly cleaning those up. This is also a good place for others to join in if you're interested—see "How to hack and contribute" below.
So, as mentioned in the previous status report, the perl6 compiler has four major components: the parse grammar, specialized parsing routines, the ast transformation, and the runtime support. Now that we're using NQP for the ast transformation, this means that the bulk of the compiler—the parse grammar and the ast transformation—are written using Perl 6 syntax. If you want to take a quick peek at these without downloading Parrot, they're currently available at:
- http://svn.perl.org/parrot/trunk/languages/perl6/src/ parser/grammar.pg
- http://svn.perl.org/parrot/trunk/languages/perl6/src/ parser/actions.pm
We're also looking into the possibility of rewriting much of the runtime support as Perl 6. One of the significant things we added this past week is the ability to embed PIR code directly inside subroutines compiled using NQP. This has turned out to be extremely useful for development—we use Perl 6 syntax for most things, but can drop in and out of PIR whenever we (temporarily) need it.
Another major item completed yesterday is a new set of routines for parsing and transforming Perl 6's quote syntax. Of course, the primary reference for this is the STD.pm grammar, and if you take a look you'll see that it's a fairly complex component because of the many options, interpolation forms, and extensions that are available. It will likely be a while before we have all of the pieces to implement quotes exactly as STD.pm has them, so in the meantime I've written up a couple of parse subroutines (in PIR) that handle most of the quoting forms and options we're likely to encounter, including interpolation. The only major forms not available at present are the «...» and heredocs, and the «...» form is waiting only on some Unicode fixes in PGE and Parrot (RT#48108).
While I'm on the topic of STD.pm and parsing: I do need to compliment Larry, Damian, and others who have been building STD.pm and the language specification for the improvements made in the language syntax over the past year or so, such as in quoting. The version of Perl 6 we have now is *much* easier to parse—by both humans and machines—than what we had a year ago.
Where things are headed next
There are two major items we will be focusing on for the next couple of weeks. The first will be continued development of the perl6 compiler—getting it back to passing the tests it was previously passing, as well as adding new features and tests. Progress on this is already being made and should accelerate nicely.
The other area of focus will be in writing a lot of prose—documents that will help new developers figure out where things are and how it's all put together. For instance, we really need a "getting started" document for perl6 that describes how to build the compiler, how to invoke it, and how/where to report bugs and patches. Much of this information is currently in the ROADMAP, but would probably be better placed in a getting started document. We also want a developer's roadmap of some sort.
I'm also planning to publish a "developer's glossary" somewhere to identify many of the various terms that get thrown around in development (PCT, PGE, NQP, STD.pm, regex, PAST, etc.).
Also on the horizon we will start looking at reviewing and possibly restructuring the Perl 6 test suite, and coming up with a mechanism to quickly update/publish the status of various language features in the compiler (hopefully with references back to the language spec).
How to hack and contribute
If you're interested in hacking on the compiler, this is a unique time to start getting involved. There are a lot of relatively easy features to be tested and added, and the discussions are about the basics of the compiler and of relatively easy features to be tested and added, and the discussions are about the basics of the compiler and how it's put together.
As mentioned above, we need a good "getting started" document, but for now here's a quick overview. First, you'll want to download and build Parrot—instructions for this are at http://www.parrotcode.org/. Once you have Parrot built, you can change to the languages/perl6/ directory and type 'make' to build the perl6 compiler. Then use the command
$ parrot perl6.pbc hello.pl
to run a hello.pl program (written in Perl 6).
To learn more about how compilers are being structured in Parrot in general, I recommend looking at languages/abc/. This is an implementation of the bc(1) language using the same tools we're using to implement perl6, with the advantage of being a lot simpler language than Perl 6. We've also tried to put a lot of comments into the source files for abc that explain what each component is doing.
After that, you can look at perl6's source code files and running some tests (either from the suite or files that you build). If you want to see perl6's intermediate compilation results, use --target=parse, --target=past, or --target=pir immediately after the "perl6.pbc" part.
In the next couple of weeks we'll be writing up the documents that describe the details of the compiler implementation, but in the meantime please ask us questions! We'll use the questions to help author the documents. The perl6 and Parrot developers tend to hang out on irc.perl.org/#parrot, and questions are welcome on the perl6-compiler mailing list.
If you find a bug or have a suggested patch, send it to email@example.com. Please use the moniker [PATCH], [BUG], or [TODO] (including the brackets) at the start of the subject so that RT can appropriately tag the item.