The Perl 6 Summary for the week ending 20030831
Welcome to this week's Perl 6 summary. This week, for one week only I'm
going to break with a long established summary tradition. No, that
doesn't mean I won't be mentioning Leon Brocard this week. Nope, this
week we're going to start by discussing what's been said on the
perl6-language list this week.
Now that's out of the way, we'll continue with a summary of the
internals list.
Continuation Passing is becoming the One True Calling Style
Jos Visser had some code that broke in an interesting fashion when
"find_lex" through an exception, so he asked the list about it. Leo
Tötsch explained that exceptions and old style subs don't play at all
well together. It seems to me that the total and utter deprecation of
subs using the old style calling conventions is not far distant.
http://xrl.us/rtk
Embedding Parrot in Perl
Luke Palmer has started to learn XS in the service of his project to
embed Parrot in Perl. Unsurprisingly, he had a few questions. He got a
few answers.
http://xrl.us/rtl
Implementing ISA
Leo Tötsch has implemented "isa". The unfashionably lowercased chromatic
argued that what Leo had implemented should actually be called "does".
Chris Dutton thought "does" should be an alias for "has". Piers Cawley
thinks he might be missing something.
http://xrl.us/rtm
More on constant PMCs and classes
Leo Tötsch's RFC on constant PMCs and classes from last week continued
to attract comments about possible interfaces and implementations.
http://xrl.us/qxk
A miscellany of newbie questions
James Michael DuPont a bunch of questions and suggestions about bytecode
emission, the JIT and about possibly extracting the Parrot object system
into a separate library. Leo supplied answers.
http://xrl.us/rtn
What the heck is active data?
Dan clarified what he'd meant when he talked about Active Data. His one
sentence definition being '"Active Data" is data that takes some active
role in its use -- reading, writing, modifying, deleting or using in
some activity'. The consequences of such data are far reaching; even if
your code has no active data in it, Dan points out that you still have
to take the possibility into account, or solve the halting problem.
Benjamin Goldberg seemed to think that you didn't need to solve the
halting problem, you could just add scads of metadata to everything and
do dataflow analysis at compile time. I look forward with interest to
his implementation.
Matt Fowles wondered why active data necessitated keyed variants of all
the ops, asking instead why we couldn't have a "prepkeyed" op to return
an appropriate specialized PMC to use in the next op. Dan agreed that
such an approach was possible, but not necessarily very efficient. Leo
Tötsch disagreed with him though.
TOGoS wondered if this meant that we wouldn't know whether "set Px, Py"
did binding or morphing until runtime. (It doesn't. "set" always simply
copies a pointer). In an IRC conversation with Dan we realised that some
of this confusion arises from the fact that "set_string" and friends
behave as if they were called "assign_string"; to get the expected
"set_string" semantics you'd have to do:
new Px, .PerlUndef
set_string Px, "some string"
Hopefully this is going to get fixed.
http://xrl.us/rto
Mission haiku
Nicholas Clark
To make some kind of mark
Committed haiku.
Don't you.
Yes, I know that's not a haiku. It's a Clerihew. I suggest that anyone
else who feels tempted to perpetrate verse on list restrict themselves
to a sestina or a villanelle, or maybe a sonnet.
I also note that POD is a lousy format for setting poetry in.
http://xrl.us/rtp
Jürgen gets De-Warnocked
Jürgen Bömmels had been caught on the horns of Warnock's Dilemma over a
patch he submitted a while back. It turns out that he'd been Warnocked
in part because both Leo and Dan thought he already had commit rights.
So that got fixed. Welcome to the ranks of Parrot committers Jürgen,
you've deserved it for a while.
http://xrl.us/rtq
Parrot Z-machine
New face Amir Karger wants to write the Parrot Z-machine implementation
and had a few questions about stuff. So far he's been Warnocked.
http://xrl.us/rtr
Notifications
Dan described how Parrot's notification system would work, and what that
means for weak references. Michael Schwern thought the outlined
notification system would also be awfully useful for debugger watch
expressions. Tim Bunce worried about some edge cases.
http://xrl.us/rts
MSVC++ complaints
Vladimir Lipskiy (who's been doing some stellar work recently on various
build issues amongst other things) found some problems trying to build
Parrot with MSVC++ and asked for help in working out how to fix them.
Jürgen Bömmels suggested a fix, which Vladimir liked in principle, but
noted that there were still some issues it didn't quite fix.
http://xrl.us/rtt
"vtable->dump"
Leo Tötsch thought that, if only for debugging, it would be really handy
for PMCs to offer a "dump" method which would return a string
representation of the PMC. Dan thought that a better approach would be
to get freeze/thaw working for PMCs and have the debugger know how to
dump a frozen PMC. This seemed to open up a whole big can of worms as
Leo, Dan and others discussed what was needed from the serialization
toolset and what its interface should look like.
Nicholas Clark threw a googly down the pitch with his description of a
possible attack on serialization schemes (possibly originating with
Jonathan Stowe) that seems deeply tricky to work around.
http://xrl.us/rtu
http://xrl.us/rtv
"exit" opcode
Leo checked in a small change to Parrot, making "exit" throw an
exception rather than simply quitting the program. Of course, unless the
exception is caught, parrot will exit anyway. He also proposed changing
the startup parameters by moving the ARGV array from P0 to P5 for
consistency with the Parrot Calling conventions. For some reason this
sparked off an enormous thread discussing how to return from the main
function.
Dan liked the the idea, so Leo checked a patch in and fixed up as many
of the examples and languages as he could find, but he expects that he
hasn't caught 'em all.
http://xrl.us/rtw
Acknowledgements, Announcements, Apologies
I'm really, really sorry about the Clerihew. But not sorry enough to
remove it.
Thanks to everyone involved in making sure I only got one and a half
of last week's predictions right. (The half prediction was to do with my
writing real Perl code, I didn't. But I *did* release the Paris code,
you can find it on CPAN at http://xrl.us/rtx if you're interested.)
Thanks to Gill for seven and 2 days (as I write this) of wedded bliss.
Check out http://xrl.us/mt4 for more of my writing (and thanks to
those who have already popped by).
As ever, if you've appreciated this summary, please consider one or more
of the following options:
* Send money to the Perl Foundation at
http://donate.perl-foundation.org/ and help support the ongoing
development of Perl.
* Get involved in the Perl 6 process. The mailing lists are open to
all. http://dev.perl.org/perl6/ and http://www.parrotcode.org/
are good starting points with links to the appropriate mailing
lists.
* Send feedback, flames, money, requests for consultancy, photographic
and writing commissions, or the soul of your first born to
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