This week on Perl 6, week ending 2003-02-02

Feb 2, 2003 by Piers Cawley

Parrot Objects (noun, not verb)

Piers Cawley worried about class private attributes and asked it it was still going to be possible to write an object serializing tool that wouldn’t require tons of Perl class overloads. Dan said that it should still be possible.

http://groups.google.com/groups

The packfile patches, an ongoing saga.

Leo Tötsch spent the week working on the packfile format and Parrot’s tools for manipulating it. Various internals folks provided feedback, pointers to standards and other handy feedback.

http://groups.google.com/groups

http://groups.google.com/groups

http://rt.perl.org/rt2/Ticket/Display.html

http://rt.perl.org/rt2/Ticket/Display.html

Securing Parrot ASM

Thomas Whateley has been thinking about how to allow Parrot to run untrusted code in a sandbox, and proposed a system where code would provide a list of required rights and Parrot would guarantee that only those privileges were provided. Matthew Byng-Maddick pointed everyone at the RFC he’d written along these lines and raised the issue of what happens when you call out to a module that’s written natively, which he described a ‘brick wall’. Others were less sure that this was a showstopper.

Somewhat annoyingly my mailer seems to have had a bad moment and lost some messages, including one from Dan in which he outlined his vision for ‘safe mode’ and gave some pointers to the VMS docs in this area.

http://groups.google.com/groups

http://dev.perl.org/rfc/353.pod

http://groups.google.com/groups – Dan’s outline

Parrot Developer World Map

Leon Brocard announced the Parrot Developer World Map, which plots the locations of all the Parrot developers who sent him their location details on a map of the world. A cursory glance at the map would seem to imply that a good place for a Parrot Developers’ face to face meeting would be a Caribbean island. Gregor neatly one upped Leon with his interactive SVG version.

http://www.astray.com/parrot/worldmap/

http://www.focusresearch.com/gregor/map.html

Coroutine context patch

Jonathan Sillito found some problems with the coroutine code, so he wrote a test exposing the errors, patched things to fix the errors and added a documentation patch to be on the safe side. Go Jonathan. Steve Fink applied the patches. Jonathan also had a question about naming, and wondered if anyone would be interested in a howto for compiler writers. Nobody commented on this, but the howto sounds like a great idea to me.

http://groups.google.com/groups

Multiple code segments and the interpreter

Leo Tötsch noted some problems with interpreter->code and multiple code segments, suggested a way forward and asked for comments. Nicholas Clark commented, wondering about the potential for memory leaks but Leo seemed to think that that was covered.

http://groups.google.com/groups

Parrot run loop problems

Leo has also been thinking about Parrot run loops and reckons we’re doing it wrong. So he proposed a different way of doing things, working through its impact on the various kinds of Parrot core. Steve Fink liked Leo’s idea, but Jason Gloudon was less sure.

http://groups.google.com/groups

Meanwhile, in perl6-language

More Array Behaviours

Michael Lazzaro is working on documenting Perl Arrays and asked for confirmations and clarifications on various areas of Array behaviour. One subthread morphed into a discussion of when to use is properties and when to use but properties. It turns out that the ‘is is compile time, but is runtime’ rule of thumb is only a rule of thumb. Damian says that a better distinction is ‘but is a property on a value, is is a property on a referent’. Variables, arrays, opaque objects, hashes etc are referents and therefore get is properties. Values are thing things that are held in variables, arrays, opaque objects etc, and they get but properties.

http://groups.google.com/groups

Spare Brackets

Martin wondered if it would be possible to use [] to do both hash and array lookups. Short answer ``No”. Which isn’t to say the thread didn’t take off like a runaway train. After far too many messages we reached the same ‘No’ conclusion that Damian had stated way back a the start of the thread. The reasoning goes like this: Given < $container[$spec]> you can’t use the type of $container to decide whether to do a hash or an array lookup because there are Perl object types which have both hash and array semantics. And you can’t use $spec’s type either because Perl happily autoconverts between numbers and strings. So, you need some way to specify what sort of lookup you need, and you do that by using {} or [] as appropriate. But, frankly, that’s beside the point. The reason we’re not using [] to do both array and hash style lookups is Because Larry Says So.

http://groups.google.com/groups

http://groups.google.com/groups

Arrays: Default values

Argh! I’ve really been screwed by problems with my mail here. For some reason a batch of mail appears to have got dropped on the floor this week and my record of this thread is the one that’s suffered the most.

The gist of the thread is that adding a default value to an array opens a whole scary can of worms to do with the distinction between ‘undef’ and ‘exists’ (made trickier still by the fact that ‘exists’ is a pretty vague concept when you’re dealing with an array.) Damian’s view is that an array with a default value should do the equivalent of

   $content = @foo[$index] // @foo.default;

ie, all undefs in the array should be ‘replaced’ with the array’s default value. And that includes any ‘deliberate’ undefs (where the programmer does @foo[$index] = undef). As I understand it, doing anything else leads to implementation pain. And it leads to even more fun when your default is computed and the function doing the computation gets passed the index as an argument. What happens when someone does a shift?

For some reason this led into a discussion of whether hashes are ordered (they’re not, but if you leave a particular hash alone any iterators (keys/values/each) will step through the hash in the same order, repeatably, but that order is not predictable).

http://groups.google.com/groups

http://groups.google.com/groups – Current ‘default’ rules

Damian Takes a Sabbatical

Damian announced that, owing to time pressures, the need to find paying work, the need to help Larry get the next Apocalypse out the door and to get the associated Exegesis written he’s unsubscribed from the language list for the time being, though he expects that he’ll probably resubscribe once A6 and E6 are released. Folks wished him well.

http://groups.google.com/groups

In Brief

After asking for suggestions of a language to implement using parrot, K Stol announced that he would be implementing a Lua->parrot compiler as his final year project.

Who’s Who in Perl 6?

Who are you?

Gopal V [gopalv82 at symonds dot net]

What do you do for/with Perl 6?

I’m more interested in Parrot rather than in Perl 6 , since it is the only really free bytecode format out there. I am planning to build a C# to Parrot compiler. I did a bunch of opcodes in this direction , but mostly what I do is lurk around in the mailing list & IRC.

Where are you coming from?

I’m from the DotGNU project and have been playing around in that code for some time. I’ve still got my foot placed firmly there and am peering over the hedge into parrot. I’m still in college, so I still have to find time to study.

When do you think Perl 6 will be released?

On a Saturday morning after announcing Tuesday afternoon in the release plan.

Why are you doing this?

It’s great to be involved with a community project , it’s a very entertaining, stimulating and educating experience. In short, I’m in this for the warm fuzzy feeling !.

You have 5 words. Describe yourself.

compulsive hacker, caffeine addict, RSI_sufferer.

Do you have anything to declare?

I promise, I’ll try hard to get the C# compiler working with parrot. (starts singing ``Some day, Some way…” off key)

Announcements and Acknowledgements

This week’s summary was once again prepared in a comfortable chair with plenty of Earl Grey tea and distractions from two delightfully ginger kittens and my embarrassing ability to screw up my Gnus installation (now unscrewed).

Thanks to Gopal V for his answers to the questionnaire this week. If you’ve been involved in the Perl 6 development process, please consider answering the same set of questions and sending them to 5Ws@bofh.org.uk and you’ll earn my undying gratitude.

Proofreading was handled by the ever lovely Aspell.

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This week’s summary was sponsored by Darren Duncan. Thanks Darren. If you’d like to become a summary sponsor, drop me a line at p6summarizer@bofh.org.uk.