Parrot - Can I use it? And how?

Question

I've had an eye on Parrot for a little while. I understand that it's a virtual machine designed to run a variety of dynamic languages, and to allow a degree of interoperability (e.g. calling a Perl function from a Python script). So, my question is in two parts:

1. Is Parrot ready for general use? I can see releases are being made, but it's not obvious whether it's something that works well now, or still a work in progress.
2. Is there any documentation on how to use Parrot? I've looked at links in previous questions, but all the documentation I can find talks about the various levels of Parrot-specific code (PIR, PASM, etc.), or how to add support for more languages. That's great, but how do I run code in existing languages on Parrot? And how do I use code written in another language?

Finally, I don't want to start a flamewar, but I know Parrot is tied up with Perl 6. I prefer Python. I understand Python is a supported language, but realistically, is it perceived as a multi-language VM, or is it a Perl 6 interpreter with other languages included as curiosities?

Discoid

Answer 1

I'm a Python developer primarily, so I'm biased. But probably in the same direction as you.

Parrot is intended to be a multi-language VM. Its Perl roots show sometimes ("0" is false, the bootstrapping language NQP is a subset of perl), but at the runtime level it's quite language-agnostic.

That said, interop between languages won't be entirely seamless. For example, the String type will most likely be used as a base by all languages, but a Ruby object will probably need wrappers (but not proxies) to act pythonic. There's no story for object interop, at least not so far.

The Python 3 compiler "Pynie" has quite a way to go. Here's the repo http://bitbucket.org/allison/pynie. Maybe you'd like to help out? Right now it's quite young, not even objects yet.

And to answer your actual question:

1. Sort of. It's not fast and the languages that target it aren't complete, but it won't crash or corrupt your memory.
2. Normally, you write code in your favourite High Level Language (Python) and compile your .py code to parrot (and from there, you can compile it to native code if you want to). Another dev can write their Perl(6) code and compile it to parrot and, if the compilers have been written with interop in mind, you'll be able to call a Perl function from python

Olenta

So, at least from a Python point of view, it sounds like it's really at the 'interesting idea, check back in a couple of years' stage? I'm afraid I don't really have an itch that I'm motivated to scratch by helping develop it, but I'm interested to see how it turns out. – Discoid

Answer 2

1. It is still work in progress, but it's mature enough for language implementors and library developers. Caveat: some subsystems are getting reworked (garbage collection, embedding), so there might be some bumps on the road ahead.

2. Each language needs a compiler that generates code Parrot understands. These compilers are released separately. (see http://trac.parrot.org/parrot/wiki/Languages ) Most languages targeting Parrot are in an early incomplete state, so interoperability isn't a big issue right now. Parrot isn't a Perl 6 interpreter, but Rakudo Perl 6 happens to be one of the most heavily developed compiler that targets Parrot.

Ceasefire