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This week's Perl 6 Summary

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From:
The Perl 6 Summarizer
Date:
May 25, 2005 10:26
Subject:
This week's Perl 6 Summary
Message ID:
m2r7fvxlmh.fsf@obelisk.bofh.org.uk
The Perl 6 Summary for the week ending 2005-05-24
    Note to self: It's generally not a good idea to go installing Tiger on
    the day you return from holiday. It's especially not a good idea to fail
    to check that it didn't completely and utterly radish your Postfix
    configuration. And your emacs. And the backing store for your website.
    And a bunch of other stuff. It's an especially bad idea not to have
    backups of things like your aliases file...

    Nor is it a good idea to get preoccupied with all these joys and
    completely forget that you're supposed to be writ ting the Perl 6
    summary.

    Ahem.

    I'm very, very sorry.

    So, on with the show.

This week in perl6-compiler
  Inline::Pugs
    Autrijus announced the availability of Inline::Pugs. If you've ever been
    moved to mix up Perls 5 and 6 in one program, your prayers have been
    answered. Just grab Pugs and Inline and you're set. Brian Ingerson made
    things even more delightfully evil:

         #!perl
         use pugs;
         sub postfix:<!> { [*] 1..$_ }
         sub sum_factorial { [+] 0..$_! }
         no pugs;
         print sum_factorial(3); # 21

    <http://xrl.us/f73s>

  Experimental Coroutine support
    Autrijus announced that Pugs now has an experimental implementation of
    coroutines. It's almost certainly not final, but it's good enough for
    exploration and feedback purposes.

    <http://xrl.us/f73t>

  Graphing tool for PerlGuts Illustrated
    Yuval Kogman asked what tool was used to generate the 'pretty diagrams'
    in PerlGuts Illustrated because he wanted to use it for diagrams in a
    forthcoming PugsGuts Illustrated. Ingy said that Gisle had hand hacked
    postscript based on initial diagrams drawn on graph paper. After some
    discussion, the plan seems to be that Yuval will just draw diagrams,
    scan them and bung them into the pugs repository. He'll rely on the
    LazyWeb to turn them into beautiful scalable graphics.

    <http://www.lazyweb.org/>

    <http://xrl.us/f73u>

  Perl Development Server
    Okay everyone, repeat after me: "Juerd is a star!"

    You may ask me why, and I shall tell you.

    Juerd and his cosponsors, Twistspace will making a Perl 6 development
    server available over the internet to any Perl 6 developers who are
    working on 'everything that improves Perl 6 development'. So, if you've
    been put off working on Pugs by the hassles of getting Haskell working
    on your machine, or if you have the kind of bandwidth that makes svn
    updates a painful prospect, worry no longer. Just sign up for a
    development account.

    There was much rejoicing and suggesting of hostnames. Rather bizarrely,
    there was also discussion of the etymology of 'sipuli' (Finnish for
    'onion' in case you were wondering).

    <http://xrl.us/f73v>

  Two releases in one day
    Autrijus announced the release of Pugs 6.2.4. About half an hour later
    he announced the release of Pugs 6.2.5.

    <http://xrl.us/f73w>

  Undef issues
    Adrian Taylor thought he'd found some issues with Perl 6's understanding
    of "undef". It turned out that he'd found some issues with his own
    understanding of same.

    <http://xrl.us/f73x>

  Method/attribute chaining
    Alex Gutteridge found some weirdness with the chaining of autogenerated
    attribute methods (I wonder if the same weirdness occurs with hand
    rolled attribute methods). So far it remains unfixed, but given the
    speed of Pugs development I doubt it'll stay that way for long.

    <http://xrl.us/f73y>

Meanwhile, in perl6-internals
  Parrot as an extension language
    Colin Adams continued to have problems using Parrot as an extension
    language for Eiffel. It turns out that interfacing between statically
    strongly typed languages and Parrot isn't easy.

    <http://xrl.us/f73z>

  Fixing t/src/manifest.t
    Dino Morelli reported problems with t/src/manifest.t and wondered how
    some of the failures came about. Jürgen Bömmels thought that the problem
    was an overzealous test -- the original version of which simply ensured
    that version control and the MANIFEST were in sync. He provided his
    suggested version of a less eager, but still svn compatible test.
    Further discussion thrashed out the various difference use cases for
    manifest checking.

    <http://xrl.us/f733>

  More t/p6rules tests
    Dino Morelli posted a bunch of tests for the Perl 6 rules. Well, he did
    once he'd done battling his mailer's somewhat bizarre choice of MIME
    type for his test files. Remember, if you're about to attach a .t file
    to a message you send to the list, make sure your mailer doesn't declare
    it to be an "application/x-troff" file -- "text/plain" is your fiend.

    Patches were applied.

    <http://xrl.us/f734>

  Stressing the hash
    Leo asked for some stress and bench mark tests for hashes because he was
    in the process of redoing src/hash.c. Bob Rogers provided one.

    <http://xrl.us/f735>

  In other news, PyPy gets an initial release
    Leo crossposted the announcement of PyPy 0.6, a Python implementation
    written in Python. It's not bootstrapping yet, but it's getting there...

    <http://xrl.us/f736>

  PIR compilers broken
    Will Coleda had some problems with with his TCL in PIR implementation.
    It turns Nick Glencross helped to track down the problems with the
    snippet he posted. I'm not sure whether his fix can be extended to work
    with the real ParTCL.

    <http://xrl.us/f738>

  MMD
    While working on mod_parrot, Jeff Horwitz ran into an issue with Multi
    Method Des patch (MMD). In particularly he didn't seem to be able to
    declare a multimethod that accepted an arbitrary PMC. Leo asked for a .t
    file so he could explore the issue further, which Jeff provided.

    <http://xrl.us/f739>

  State of ParTCL
    Will Coleda posted a summary of the current state of ParTCL. By the
    sound of things, it's getting there.

    <http://xrl.us/f74a>

Meanwhile, in perl6-language
  Virtual methods
    Whilst noting that Perl 6 doesn't really need to be able to declare
    methods as virtual in the same way as C++, since one can simply use the
    handy "..." to do the job, Aaron Sherman noted that there was a case for
    something similar when declaring 'stub' methods that could be overridden
    by Roles. The idea being that you would implement an initial behaviour
    that could be further decorated by a Role. Except, as Luke pointed out,
    the Roles system as currently defined treats all such methods as
    overridable.

    Aaron wasn't sure that this was such a good idea, and produced code to
    illustrate why.

    <http://xrl.us/f74b>

  Default precedence of user defined infix ops
    Ingo Blechschmidt pointed out that user defined infix operators work in
    Pugs now. He wondered what their default precedence should be and how to
    explicitly define the precedence. Luke came forth with an answer, Sam
    Vilain asked an evil question, and Damian Conway suggested that, given
    how drastically precedence weirdness can mess with a programmer's head,
    there shouldn't be a default precedence at all, and if there were, it
    should be looser than "infix:<+>". I agree with Damian.

    <http://xrl.us/f74c>

  "1,(2,3),4)[2]"
    Argh! My head hurts!

    However, if you're not sure how context works in Perl 6, Juerd provides
    a really good summary later in the thread

    <http://xrl.us/f74e>

    <http://xrl.us/f74f> -- Juerd explains context

  Reduce metaoperator on an empty list
    Matt Fowles wondered how the shiny new reduce metaoperator worked given
    an empty list. Various suggestions were forthcoming, but I lean towards
    Randal's "inject" solution -- but I'm a Smalltalk fan, so no surprise
    there. Personally, I reckon that the metaoperator version should just
    return undef given an empty list -- if you want anything clever you
    should eschew the syntactic sugar and use "inject" or something like it.
    It seems that the consensus is leaning towards using an "identity"
    attribute on the infix operator.

    BTW, what happens when you apply "[/]" to a list with one element?

    <http://xrl.us/f74g>

  Complex Arithmetic
    Doing complex arithmetic right in a programming language is tricky.
    Edward Cherlin wondered if Perl 6 should follow what seems to be the
    consensus among programming languages that care about this sort of thing
    and use the shared definitions used by APL, Common LISP and Ada. Luke
    thought it might be best left to C6PAN. (The discerning language
    designer's equivalent to paying no attention to the man behind the
    curtain methinks).

    <http://xrl.us/f74h>

  Syntax for specifying role parameters
    Ingo Blechschmidt wondered if the syntax for specifying role parameters
    should be the same as the standard subroutine signature syntax (with a
    slightly modified proposed meaning for ":"). Thomas Sandlaß had some
    related suggestions to add. Nothing from any of the design team yet.

    <http://xrl.us/f74i>

  "./method"
    Martin Kuel can't make himself like "./method" as a shortcut for
    "$whatever_you_call_self_this_week.method". Frankly, I can't blame him.
    But then I continue to think that the originally specified semantics of
    ".method" (calls method on $_, whether in a method or a sub, or anywhere
    else for that matter) are fine.

    <http://xrl.us/f74j>

  "uniq"
    Ingo wondered why "uniq" wasn't in the current draft of Synopsis 29. He
    also wondered if its default comparator should be "=:=". It turns out
    that there's rather more to the semantics of "uniq" than you'd expect;
    Damian's 'hyper correct' implementation blew my mind.

    <http://xrl.us/f74k>

  "s/.../{ $junction }/"
    Junctions? In substitutions? What is Ingo thinking? Warnock applies.

    <http://xrl.us/f74m>

  Argument type checking
    Joshua Gatcomb sought reassurance that

        sub foo (Int $bar) { say $bar }
        foo 'hello';

    would do the right thing, namely throw an exception. Luke reassured him.

    <http://xrl.us/f74o>

  How to create a new meta operator
    Ingo's obviously been in a very wondering mood this week. This time he
    wondered if he could create a new meta operator in the obvious (to
    anyone who's read Apocalypse 12 carefully) way. What? You've not read
    Apocalypse 12 carefully? Shame on you! Like this:

        sub infix_circumfix_meta_operator:{'->', '<-'} (Code &op, $left, $right)
          { op $left + 1, $right + 1 }

        say 2 ->+<- 3; # 7

    Luke thought so, but threw in his own question about how we'd specify
    meta operators that only work on particular classes of operators.

    <http://xrl.us/f74p>

  How to invoke a method reference
    Continuing to mine his wondering vein, Ingo asked how to invoke method
    references. Juerd thought it'd work pretty much as it does in Perl 5.

    <http://xrl.us/f74r>

  Junctive and Higher order Types
    Sam Vilain's question about converting a Haskellish chunk of code into
    Perl 6 was Warnocked.

    <http://xrl.us/f74s>

  "foo(1: 2: 3: 4:)"
    I was *so* tempted to use 'Multimethod colonoscopy' as the heading for
    this section. Aren't you glad I resisted?

    Autrijus has started to implement multi-level invocants in MMDs. He
    asked a bunch of sanity check questions before proceeding. Luke and
    Damian provided the sanity.

    <http://xrl.us/f74t>

  Lazy context
    Borrowing Ingo's wondering hat, Yuval Kogman had questions about the
    semantics of laziness. Laziness is one of many features of Perl 6 that's
    reasonably easy to understand from the point of view of the user, but
    which is a big old can of worms from the point of view of the
    implementer. I think I understood Yuval's proposed
    semantics/implementation, but I'm stumped when it comes to summarizing
    it. People seemed to like it though.

    <http://xrl.us/f74u>

  Declaration of "my()" variables using symbolic referentiation
    Snatching back his wondering hat, Ingo asked a question I didn't
    understand about declaring "my" variables using symbolic referentiation.
    Frankly, I don't even understand the subject. The consensus of those
    responding seemed to be that what Ingo wanted to do was pretty silly in
    the first place.

    <http://xrl.us/f74v>

  Explicit laws about white space in rules
    Jeff 'japhy' Pinyan wanted to know what the rules were about where white
    space is permitted in rules. In particular, was it legal to write "\c
    [CHARACTER NAME]", or must he write "\c[CHARACTER NAME]". Damian reckons
    only the second is legal.

    <http://xrl.us/f74w>

And we're done
    That's it for another week. Tune in at the same time next week when Mr
    Fowles will entertain you all with his interpretation of the coming
    week's events. I'll be back here the week after that.

    If you find these summaries useful or enjoyable, please consider
    contributing to the Perl Foundation to help support the development of
    Perl.

    <http://donate.perl-foundation.org/> -- The Perl Foundation

    <http://dev.perl.org/perl6/> -- Perl 6 Development site

    Or, you can check out my website. Maybe now I'm back writing stuff I'll
    start updating it.

    <http://www.bofh.org.uk/>

    Vaguely pretty photos by me can be found at:

    <http://xrl.us/f74x>


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