This Week in Perl 6, July 13-19, 2005
by Piers Cawley
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Pages: 1, 2
Meanwhile in perl6-language
MML Dispatch
The ongoing discussion of the right way to dispatch multimethods is still, um, going on. Damian and Luke appear to have a fundamental disagreement about what the Right Thing is. "Manhattan!" "Pure!" "Manhattan!"--it's not quite that bad, but they seem to have entrenched positions. Elsewhere in the thread, Larry mused on which was more general, classes or roles. Thomas Sandlaß wondered how they stood in relation to types.
Your summarizer wondered how he was ever going to explain all this and punted.
Method
Calls on $self
My eyes, they burn! At this rate, I'm simply going to use $?SELF
in all my Perl 6 classes. Larry's latest suggestion seems to please even fewer
people than ./method, which is really saying something. As someone
who's not a fan of ./, I found myself slightly surprised to agree
with Autrijus, who reckons you get used to it really quickly.
The Perl 6 Library System
In response to a question from Autrijus about coderefs in @INC,
or whatever Perl 6 is going to call it, Larry mused on the possible eventual
design of Perl 6's library system. It seemed to me that he was dropping a
rather heavy hint to any interested readers who might like to come up with a
first cut of Perl 6's library system.
Later, he did some thinking aloud about treating strings as arrays, or vice versa.
Method Resolution Order
Stevan "MetaModel" Little cheered Larry's statement that methods, subs, submethods, and "anything in between" all live in the same namespace. If you want to give two code-like things the same name, then you must explicitly declare them as multi.
Stevan went on to ask a bunch of questions about the semantics of method resolution, so as to get the Perl 6 MetaModel working right. Discussion ensued.
Type::Class::Haskell
Does Role
I haven't the faintest idea what Yuval Kogman is talking about. Dammit, I need to learn Haskell now. Luckily, Autrijus, Luke, David Formosa, and Damian did seem to understand it. There was ASCII art and everything. Sadly, there's no Unicode art, but it's only a matter of time.
Optimization Pipeline
Yuval Kogman posted an outline of the optimization pipeline idea that he'd brought up in a Hackathon. If confess that it looks rather like something discussed a few months (years?) ago that Chip shot down rather convincingly. (I remember this because I took pretty much the same position as Yuval, and I really didn't want to be convinced.)
STM Semantics, the Transactional Role
Yuval Kogman discussed some issues with Software Transactional Memory (STM). A short discussion ensued.
More Method Resolution Order Questions
Returning from reading up on method resolution orders and class precedence lists, Stevan Little had a pile of questions and suggestions about Perl 6's method resolution semantics. He pushed for using "C3" as Perl's algorithm of choice and is implementing it in Perl6::MetaModel until and unless @Larry decides differently. He's off to a flying start in that the One True Larry thinks it's a good idea.
Accessor-Only Virtual Attributes
Sam Vilain wondered what would happen if he made an "accessor" for an
attribute that didn't really exist. He wanted to be able to disguise accessor
methods as attributes within class and subclass scope (at least, I think that's
what he wants). Larry seemed to think he was barking up the wrong tree--class
attributes are only likely to be accessible using the $.whatever
form within their declaring class and not any subclasses. Larry's "got some
driving to do" so expect some more thoughts about this in the next summary.
Strange Interaction Between Pairs and Named Binding
Autrijus noted that, although
for [1..10].pairs -> Pair $x { say $x.value }works,
for [1..10].pairs -> $x { say $x.value }doesn't, which is somewhat counter-intuitive. The problem is, the second cas
treats the pair as a named argument specifier. After discussion, Autrijus
suggested that the best thing might be to specify that the Bare
code object (which includes pointy and non-pointy blocks) have Any
as a default parameter type--essentially turning off the special behavior of
pairs when calling named blocks. I'm all for this myself, but Larry has yet to
speak.
How Do Subroutines Check Types?
Ingo Blechschmidt had some questions about specifying types in subroutine
definitions. Specifically, he wanted to be able to specify that a sub only take
instances of a class Foo and its subclasses but not the class Foo (or its
subclasses) itself. Thomas Sandlaß thought that what Ingo wanted is the
default behavior and you actually have to do some work to get it to behave any
other way.
Referring to Package Variables in the Default Namespace
Matthew Hodgson asked for some clarification of how the default package namespace works. Apparently, Pugs and Synopsis 10 are slightly at odds. Larry had some answers. Matthew probably has some more questions.
Crikey! That Went Quickly
Or, for the traditionalists among you:
Acknowledgements, Adverts, Apologies and Alliteration
Hunting the Perfect Archive
I'm still on the lookout for a replacement for Google groups for my message
links. I need an archive that's up to date with the lists, and has URLs that
are easy to derive from Message-IDs. Bonus points for good thread handling.
Help Chip
Tell all your friends, this cannot stand.
The Usual Coda
If you find these summaries useful or enjoyable, please consider contributing to the Perl Foundation to help support the development of Perl.
Or, you can check out my website. Maybe now I'm back writing stuff I'll start updating it. There are also vaguely pretty photos by me.
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