The Perl 6 Summary for the week ending 20021020
I'm sorry to have to inform you that I've returned from my holiday (no,
base jumping and paragliding were *not* involved) and that this week's
summary will not be written by the estimable Leon Brocard. Sorry about
that. Leon is currently taking a rest cure.
So, with the customary mention of Mister Brocard out of the way good and
early this week, it's time to take a look at what's been discussed on
the internals list:
Regarding JVM - Parrot Compatibility
Newcomer Karthik Kumar is interested in writing a tool to convert java
".class" files to parrot ".pbc" files and asked for information on what
had been done in this area. Leon Brocard says it's very easy to get the
basics working because of the low number of JVM bytecodes. But getting
the fundamentals (classes, objects) right is hard. Ramesh
Ananthakrishnan commented that it might be a little early for anything
more than proofs of concept at the moment as Parrot is a rapidly moving
target. Ramesh also came up with the idea of compiling `real machine'
assembly language to `virtual machine' parrot assembler.
Karthik commented that the real issue seems to be one of what level of
support Parrot will offer for objects, and until that is known the
class->parrot problem is almost pointless to solve.
http://makeashorterlink.com/?S18F26432
http://makeashorterlink.com/?C19F22432 -- Ramesh clarifies his `Linux
in Parrot' idea.
The Getting Started Guide
Erik Lechak is still not loving POD but, despite his distaste he posted
version 0.4 of his getting started guide in POD format. Thanks a lot
Erik. Marty Pauley suggested that Erik take a look at the Simple
Document Format which may meet his needs better than POD
http://makeashorterlink.com/?F2AF11432
http://makeashorterlink.com/?Z5BF34432
C# and Parrot
Rhys Weatherly, author of Portable.NET, part of the DotGNU project made
a welcome appearance on the list. Apparently the DotGNU people are
looking into compiling C# down to parrot bytecode and hoped that there
might be parrot people who were interested in trying to complete their
compiler and system library.
Rhys wanted to know how to make a user-defined class in Parrot; what the
convention is for which registers must be saved across a call; the size
of "int" and whether there was a way to store and access auxiliary data
in a Parrot bytecode file.
Answers were provided. Sadly, the answer to Rhys's question about
user-defined classes was "You don't, yet." Other answers were more
immediately useful.
The DotGNU weekly IRC meeting discussed Parrot this week, Leon and Dan
managed to cover both sessions between them, and there's a log
available.
http://makeashorterlink.com/?M2CF21432
http://makeashorterlink.com/?J1DF11432 -- Condensed summary of the
meeting
http://ajmitch.dhis.org/dotgnu/ -- unedited logs available here
Variable/Value Split Prelims
Leopold Toetsch rather confused me when he replied to a two week old
message (I thought I'd completely screwed up setting the `limit by date'
values in my summary buffer) about the conceptual split between
variables and values. Leo wanted some clarification which Dan provided.
http://makeashorterlink.com/?M4EF21432 -- Dan's old message
http://makeashorterlink.com/?C3FF22432 -- Leo's questions
PMC Initializers
Leon Brocard attempted to kick start discussion of Jonathan Sillito's
patch to pass more information when creating new PMCs. Leopold Toetsch
and Josef Höök both said they thought that something along those lines
was a good idea, but the discussion seemed to die there. Later in the
week, Dan introduced the new "init_pmc" function to PDD02, which works
along the lines suggested.
http://makeashorterlink.com/?V20023532
http://makeashorterlink.com/?I11021532
PerlHash questions
Clinton A. Pierce wondered about how to do the equivalent of "exists
$hash{$key}" in Parrot when one doesn't necessarily know the types of
the things in the hash. Leo Toetsch pointed to "exists_keyed" and
"type_keyed". Jason Gloudon pointed out that the docs for "type_keyed"
referred only to PMCs, with no mention of 'primitive' types. He wondered
if PerlHash shouldn't just dictate that its contents were all PMCs.
http://makeashorterlink.com/?M62042532
Meanwhile in Perl6-language
The language group is trying to catch up with internals in number of
posts. They managed 89 posts this week compared to internals' 96. If you
discount attachments, language probably won on volume (and it certainly
wins hands down on the `difficulty of summarization' metric).
Draft Proposal: Declaring Classwide Attributes
The discussion of how to declare classwide attributes rumbled on from
last week; I'll just pick out a few nuggets.
* "HASH", "ARRAY" etc will likely become "Hash", "Array" etc, and
there's a good chance that "UNIVERSAL" will become "Object"
* Implicit invocants can participate in multiple dispatch
* It's worth taking a look at Smalltalk metaclasses, or Ruby's classes.
* "Putting Metaclasses to To Work" might also be worth a read
http://makeashorterlink.com/?X13021532 -- Thread starts here
http://makeashorterlink.com/?P64013532 -- the Metaclasses book
Perl6 Operator Precedence Table
The `Operator Precedence' thread kept on rolling from last week. The
current game appears to be `working out how to free "&" and "|" to
become superposition constructors', which means hanging the bitwise
operators somewhere else. Various ideas have been proposed, but people
really didn't like "|||" and "&&&". The current front runners appear to
be:
* "$a b& $b"
* "$a .& $b"
*
my @a is bitmap($a);
my @b is bitmap($b);
my @c is bitmap($c);
@a = @b ^|| @c; # Correcting what I assume is Larry's typo
It looks like this whole area is still somewhat fluid though.
http://makeashorterlink.com/?B55022532
http://makeashorterlink.com/?S26053532
http://makeashorterlink.com/?M27021532
"untaintby" property
Miko O'Sullivan proposed an "untaintby" property which `restricts which
modules may untaint the data or data derived from that data.' The
feedback wasn't that positive, but Larry came up with the idea of
callbacks on properties which look rather cool. (`too cool!' according
to Miko).
http://makeashorterlink.com/?W28062532
http://makeashorterlink.com/?L19022532
Indeterminate Maths
Michael Schwern opened a can of worms when he wondered if "1/0" would
throw an error or just return a value representing an indeterminate
result. Leon wondered if it'd be possible to, for instance have a module
which did all its arithmetic in, say, integers module prime P. Dan
thought yes, with lots of overloading. Adam Lopresto thought "1/0" would
be a good place for the new "fail" semantics. We ended up in a debate
about the mathematical values of "$n/0" (apparently x/0 is indeterminate
when x is zero and undefined otherwise).
This thread also saw discussion of: the nature of Object Orientation and
the benefits of instance based inheritance; the semantics of NaN. (Did
you know that "NaN != NaN"; the use of exceptions; proofs that 1/0 is,
necessarily, undefined; Lukasiewiczian logic (SQL type NULLs); Miko's
`inner Larry Wall'; and the hypothetical "Math::Perverse" module, which
sounds like a candidate for the Acme namespace to me.
Larry seems to think that a combination of pragmas and overloaded
classes should be enough to do the job.
http://makeashorterlink.com/?J5A012532
http://makeashorterlink.com/?Q3B042532 -- complete with citation of
www.userfriendly.org
A concept for Exceptions
Miko O'Sullivan has been doing some serious thinking. After wowing us
with his "untaintby" proposal, he came up with some proposals for
exceptions which would allow for all sorts of cunning tricks. Dan
pointed out that at least one of the cunning tricks wasn't actually
possible, but that you could get something like it by throwing
continuations with your exceptions.
http://makeashorterlink.com/?N2C064532
In brief
The effort to fix the JIT core when compiled with optimizations on x86
boxes continues (with a certain amount of discussion of how to use the
test modules).
Simon Glover sent a covey of patches, mostly adding tests (yay!) along
with one to fix up and document the ".include" assembler macro. Applied.
Chromatic did some copy editing of the docs and sent in a patch with his
fixes. Applied.
Leopold Toetsch has a large patch for the GC system which tries to deal
with some of the problems. It's not a complete fix, but Leo thinks it's
a start.
Simon Glover noticed that lib/Parrot/PMC.pm is marked as autogenerated
and therefore removed by a "make clean", which would be okay, but
there's no rule in the makefile to regenerate it. Steve Fink fixed it
using Simon's suggested solution.
Dan's fixed the docs for the splice vtable entries in PDD2. Leopold
Toetsch promised to implement it.
Michael Lazzaro offers a summary of variables and assignment at
http://cog.cognitivity.com/perl6/var.html. Thanks Michael.
Who's Who in Perl 6
Who are you?
Brent Dax
What do you do for/with Perl 6?
I manage Configure changes and occasionally work on embedding and
extending, the regex engine, misc.c, or whatever catches my fancy.
Where are you coming from?
The end of a day in high school (or sometimes the middle of the
day...) :^)
Seriously, I think Perl 6 is an excellent idea. Perl is a great
language, but it's been in need of a de-crufting for some time.
When do you think Perl 6 will be released?
Hmm...probably next year sometime. Not soon enough for me to like
it, but not late enough to complain about it.
Why are you doing this?
Because it's fun and interesting. And I get paid to manage a Web
site, so Perl eq money. And I'm actually taken seriously.
You have 5 words. Describe yourself.
Hubristic hacker who really knows_little.
Do you have anything to declare?
No, of course not. No need to search this suitcase. Nope, not a bit.
The customs dogs must have smelled a doggy treat or something.
Acknowledgements
Thanks are, of course, due to Leon Brocard for ably filling my shoes for
the past couple of weeks and making sure that the summaries got through.
I'd also like to thank Rhys Weatherly and Gopal V for popping up on the
internals list. I think it's *great* to see good communication and
cooperation between the different projects working in this field.
Thanks too to my army of crack proofreaders who help to turn the
misspelled morass of bad grammar that is my first draft into something
that's readable. This week's team was: Chris Ball
The Perl 6 Summary was produced with the aid of GNER tea, the
distractions of MAME and *10 Yard Fight* and with money from O'Reilly
and Associates. If you liked it, please consider giving money to the
Perl Foundation at http://donate.perl-foundation.org and feedback
and/or NeXTcubes to me, <mailto:pdcawley@;bofh.org.uk>.
The fee paid for publication of this summary on perl.com has been
donated directly to the Perl Foundation.
--
Piers
"It is a truth universally acknowledged that a language in
possession of a rich syntax must be in need of a rewrite."
-- Jane Austen?
