The Perl 6 Summary for the week ending 2005-04-26
It's my turn again. What fun.
"What," I hear you all ask, "has been going on in the crazy mixed up
world of Perl 6 design and development"? Read this summary and,
beginning with perl6-compiler, I shall tell you.
This week in perl6-compiler
Refactoring Test.pm
Stevan Little had an idea while he was refactoring Test.pm. He wondered
whether to get rid of the various "todo_*" functions in favour of just
using a t/force_todo file. Which led him to wonder about doing away with
t/force_todo in favour of a "force_todo()" function. He asked for
opinions before he started making the change (which isn't exactly a
refactoring).
General opinion seemed favourable, though I confess I am perturbed by
the proposed release trick of proclaiming all failures, whether expected
or not, to be TODOs. The current system generates an explicit list of
tests that are failing on 'core' systems. The proposed solution would
seem to make all failures equal, so even unexpected 'platform' failures
wouldn't be caught.
<http://xrl.us/fwkn>
Weird thing with say ++$
What do you know, "say $i++, ++$i" behaves weirdly.
<http://xrl.us/fwko>
Pugs 6.2.1 released
Autrijus announced the availability of Pugs 6.2.1 which comes complete
with much shininess.
<http://xrl.us/fwkp>
This week in perl6-language
Parrot Common Lisp
Cory Spencer's port of Common Lisp to Parrot was much admired (it's got
some way to go before it's *really* Common Lisp, but it's a cracking
start). Uwe Volker suggested porting emacs to it and was promptly
accused of being Erik Naggum by Lars Balker Rasmussen.
Cory acquired (or is acquiring) a committer bit.
<http://xrl.us/fwkq>
State of the Tcl
Will Coleda gave the list a heads up on the state of ParTCL, the Parrot
TCL port. It's still failing some tests, apparently because of GC
issues.
A few days later, these problems went away (we're not quite sure how
though).
<http://xrl.us/fwkr>
<http://xrl.us/fwks>
"alarm()" and "later()"
Leo stated that Parrot provides subsecond timer resolution as well as
alarm callbacks and multiple timers. Hurrah!
<http://xrl.us/fwkt>
RFC "assign Px, Py"
Leo posted a discussion of the semantics of "assign" and "set", with a
proposed change to PIR syntax. Warnock applies.
<http://xrl.us/fwku>
RFC unary operations
In another RFC, Leo discussed changes to Parrot's unary operators and
proposed other changes.
<http://xrl.us/fwkv>
One more MMD -- assignment
Dan noted that he was writing a great deal of code in his "set_pmc"
vtable methods that looked very MMD-like. He suggested that adding
assignment to the list of MMD functions might be a good idea. Leo
pointed him at his assignment RFC.
<http://xrl.us/fwkw>
Fun with "morph()"
Nicholas Clark wondered about the responsibilities of the "morph" method
with respect to handling "PMC_struct_val". In the subsequent discussion
it became apparent that "morph" can get complicated. Bob Rogers supplied
a bunch of extra complications and wondered about the feasibility of
making Parrot morph-free. Leo agreed that it seemed feasible and is
probably a good idea. Another subthread made my head hurt -- I can
understand this stuff much better when I'm sat 'round a table with
people and we're kept supplied with drinks, notepaper and, in Leo's
case, industrial quantities of tobacco. (Ah... YAPC::Paris!)
<http://xrl.us/fwkx>
Building an incomplete code generator into Parrot
[EMAIL PROTECTED] (that's the only name I have) has started work on
implementing a JIT backend for the AMD64 processor. He asked a few
questions and Leo provided answers.
<http://xrl.us/fwky>
Calling Convention Abstraction
This thread continues to rumble on. Leo said that what he wants is for
the HLL folks to create a workable scheme for abstract and extendable
calling conventions that could express all the various HLL specific
semantics of function calling, pointing out that, unless we have this we
can forget interoperability (or at least, easy interop).
<http://xrl.us/fwkz>
Alpha development Box
Bob Rogers 'has' an Alpha development box that can be used for open
source projects. He wondered if the Parrot project could make use of it,
and if so what was the best way of doing this. Some discussion occurred
on the list, but I assume (hope) more happened offline.
<http://xrl.us/fwk2>
Meanwhile, in perl6-language
Calling junctions of closures
Brad Bowman wondered about calling junctions of closures. He guessed
that the rule is "call 'em all and return a similarly structured
junction." but wasn't sure. Thomas Sandlaß wasn't so sure.
My head hurts.
<http://xrl.us/fwk3>
"{ => }" autocomposition
Autrijus asked about the following fragment:
%ret = map { $_ => uc $_ }, split '', $text;
which gives Pugs a massive headache.
From the ensuing discussion, it appears to cause Larry and Autrijus
headaches too. Also, it turns out that Larry's Perl 5 to Perl 5
translator has both madprops and madskills. Hurrah! Darren Duncan
suggested that
%ret = map:{ $_ => uc $_ }, split '', $text;
should serve to say that the block is to be treated as a block rather
than a hash constructor. He thought that that came from one of the
synopses, but couldn't remember which.
I wonder if
%ret = map -> {$_ => uc $_}, split '', $text;
wouldn't do the job. (Or did the syntax change on me when I wasn't
looking?)
<http://xrl.us/fwk4>
Embedding languages in Perl 6
BÁRTHÁZI András had some questions about introducing different parsing
rules in the middle of a Perl 6 program. Larry's answer was, essentially
"All's fair if you predeclare", but with an interesting idea about using
"`" as a way of introducing a 'self-terminating construct', so one could
do:
use XML;
$a = `<elems><elem>Content #1</elem><elem>Content #2</elem></elems>;
or
use SQL;
$a = `select * from table`;
Various possibilities were discussed, but nothing got set in stone.
<http://xrl.us/fwk5>
Closure/block/sub multiplier
Matt Creenan wondered about doing "@names = &get_next(...) XX 5;"
(which, obviously, would call &get_next five times and shove the results
into @names). Juerd pointed out some subtleties to do with functions
that return closures. Later in the thread he decided that he controlled
both the horizontal and the vertical, with particular reference to
redefining true, false and undef.
<http://xrl.us/fwk6>
"alarm()" and "later()"
Remember the discussion of "alarm" and "later" in perl6-internals? It
moved over to perl6-language. Larry agreed that Perl 6's time interfaces
would favour floating point time values, but he wasn't quite sure if any
of them would be called "alarm". Discussion ensued, both on the topic
and matters of naming style.
<http://xrl.us/fwk7>
$?OS globals, etc
Scott McWhirter proposed making the various $?OS etc variables into
attributes of some GLOBAL class. Larry thought it was a good idea, but
wasn't sure it was entirely right as proposed; this area is still being
designed.
<http://xrl.us/fwk8>
Parens vs. subroutine parameter
Autrijus had a question about how function signatures and various forms
of paren magic interacted. He, Juerd and Larry thrashed things out.
<http://xrl.us/fwk9>
"-X"s auto-(un)quoting
Michele Dondi had some questions/suggestions about the various file test
operators. Larry answered and the thread spun off into a discussion of
all sorts of aspects of these handy operators. Well, that was before it
turned into a discussion of the semantic of <.foo>, or was that "^foo",
or maybe "_foo", or possibly "....foo". At this point, things got a
little heated. There's no decision as yet (personally I'm a fan of the
scheme as originally proposed; ".foo" calls the method foo on the
current topic, whatever that may be. If you need to hang onto old
topics, give them a name. I appear to be in something of a minority).
<http://xrl.us/fwma>
Unify cwd
It turns out that the 'current working directory' isn't as obvious as it
sounds. It also turns out that Larry would like to be able to pretend
that it is until it turns out not to be.
<http://xrl.us/fwmb>
Blocks, continuations and "eval"
When last we saw this thread, Larry had said that continuations would be
available in Perl for people who ask specially, but wouldn't be left
lying around in the open where 'some poor benighted pilgrim might trip
over them unaware'. Wolverian asked what the interface would be. Larry
thought it would probably start "use Continuations;", or possibly "use
CONTINUATIONS;".
The thread prompted Stéphane Payrard to ask about the possibility of
some of the more 'out there' functional programming tricks making it
into Perl 6. Once again, all's fair if you predeclare, but it looks like
Perl 6 already has core access to some pretty out there stuff.
<http://xrl.us/fwmc>
Accepted abbreviations
Juerd wondered if we could compile a list of standard abbreviations for
various terms so that they can be consistently applied. He kicked off
with a list of his own. There was some discussion but I somehow doubt
his list will be used rigorously.
<http://xrl.us/fwmd>
Thunking semantics of ":="
Once someone starts to implement a language, you get a wonderful driver
for design decisions that need to be made and ambiguities to be ironed
out. On this occasion, Autrijus needed some clarification of the
semantics of the binding operator, ":=". Ambiguities were ironed, and
implementations were written (and yes, I *do* mean implementations).
<http://xrl.us/fwme>
"for all(@foo) {...}"
Brad Bowman had questions about the workings of "for all(@foo) {...}"
based on S03. It turns out that the synopsis is wrong. Larry explained
how it's supposed to work (which is how it already works in Pugs).
<http://xrl.us/fwmf>
Lazy Lists + Mutable Arrays + Garbage Collection
Brad also had questions about the workings of lazy lists. In particular,
he wondered about treating streams as mutable arrays. Warnock applies.
<http://xrl.us/fwmg>
"map { $_ => uc $_ }, @foo" again
Autrijus proposed a cunning plan to deal with the ambiguities inherent
in:
map { $_ => uc $_ }, @foo;
by suggesting that using a block without the comma should force said
block to be interpreted as a block rather than a hash constructor. Larry
wasn't sure, arguing that it were best to disambiguate with something
just before, or just inside the block (in the same way that pattern
modifiers now go before the pattern).
<http://xrl.us/fwmh>
Passing hash to a sub expecting named params
Carl Franks wondered if he could pass a splatted hash (*%hash) to a
function that expects named arguments. Answer, yep.
<http://xrl.us/fwmi>
Turning off warnings for a function's params?
David Storrs wanted to be able to turn off selectively turn off some
warnings when he's testing. He asked how to go about doing it. Luke and
Juerd provided some answers.
<http://xrl.us/fwmj>
How do I... tie hashes/arrays
Discussion of how to tie hashes and arrays continued.
<http://xrl.us/fwmk>
Surprising consequences
Juerd worried that code like "if($foo) { say 'foo'}" would throw syntax
errors. It turns out that one of his givens wasn't quite as given as he
though. So it's not a syntax error.
<http://xrl.us/fwmm>
Calls and parens
Juerd posted a set of examples of the new rules for parsing parentheses
in function calls and asked which of his assumptions were wrong. Luke
Palmer reassured him.
<http://xrl.us/fwmn>
Context and index expressions
Autrijus posted a set of examples of array indexes and asked if he'd got
all the contexts right. There was no answer at the time of writing.
<http://xrl.us/fwmo>
Hmm... still fun. I could get used to this.
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/fwmp>
See you all in a fortnight.
