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Parrot is a grandiose idea that turned out to be more realistic than anyone originally could have believed: why not have a single interpreter for several languages? Unlike the parent Perl 6 project, which was launched in a single day, the plan for Parrot formed in bits and pieces over the space of a year.
On April 1, 2001, Simon Cozens published an article titled "Programming Parrot "as an April Fools' joke (http://www.perl.com/pub/a/2001/04/01/ parrot.htm). It was a contrived interview with Larry Wall and Guido van Rossum detailing their plans to merge Python and Perl into a new language called Parrot. A few months later, when Perl 6 internals began to take an independent path within the larger project, they dubbed the subproject "Parrot" in a fitting turn of life imitating art.
The plan for Parrot was to build a language-neutral runtime environment. It would support all the features of dynamic languages such as Python, Ruby, Scheme, Befunge, and others. It would have threading and Unicode support (two of the most problematic features to add into Perl 5 code) built-in from the start. It would support exceptions and compilation to bytecode, and have clean extension and embedding mechanisms.
The language-neutral interpreter was originally just a side effect of good design. Keeping the implementation independent of the syntax would make the code cleaner and easier to maintain. One practical advantage of this design was that Parrot development could begin even though the Perl 6 language specification was still in flux.
Early Steps Toward Perl 6 InternalsThe earliest progress toward implementing Perl 6 started before the current incarnation of Perl 6 was even conceived. The Topaz project, started in 1998, was spearheaded by Chip Salzenberg. It was a reimplementation of Perl 5 written in C++. The project was abandoned, but many of the goals and intended features for Topaz were adopted for Perl 6 internals, and the difficulties Topaz encountered were also valuable guides. Sapphire was another early prototype that influenced the shape of Perl 6 internals. It was a one-week project in September 2000. The brainchild of Simon Cozens, Sapphire was another rewrite of Perl 5 internals. It was never intended for release, only as an experiment to see how far the idea could go in a week, and what lessons could be learned. |
The bigger win in the long term, though, was that since Parrot would support the features of the major dynamic languages and wasn't biased to a particular syntax, it could run all these languages with little additional effort.
It's generally acknowledged that different languages are suited to different tasks. Picking which language will be used in a large software project is a common planning problem. There's never a perfect fit. It usually boils down to picking the language with the most advantages and the least noticeable disadvantages. The ability to combine multiple languages within a project could be a huge benefit. Use well-tested libraries from one language for one task. Take advantage of a clean way of expressing a particular problem domain in a second, without being forced to use it in areas where it's weak. The modular design also benefits future language designers. Instead of targeting lex/yacc and reimplementing low-level features such as garbage collection and dynamic types, designers can write a parser that targets the Parrot virtual machine.
The internals development for Perl 6 falls to the Parrot project. Dan Sugalski leads the project as internals designer, and Steve Fink is the current pumpking. The Parrot project is largely autonomous. Dan coordinates with the rest of the design team to ensure that Parrot will be able to support the semantics Perl 6 will require, but the language designers have very little input into the details of implementation. Parrot isn't developed solely for Perl, but Perl 6 is entirely dependent on Parrot - it is the only interpreter for Perl 6.
The core communication line for the Parrot project is the mailing list, perl6-internals@perl.org, otherwise known as "p6i." It's a much more business-like list than p6l. Workflow in Parrot takes the form of submitted patches. Anyone is free to submit a patch, and contributors who consistently submit valuable patches over a long period of time are granted check-in access to the CVS repository.
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Created: March 27, 2003
Revised: August 23, 2003
URL: http://webreference.com/programming/perl/essentials/chap1/1
