This Week in Perl 6, May 3, 2005 - May 17, 2005


Welcome ot another fortnight’s summary. Wouldn’t it just figure that I can’t think of anything sufficiently non-sequiterish to amuse myself. Perhaps I need a running gag like Leon Brocard or chromatic’s cummingesque capitalization. Maybe I should start one and not tell you. That could be fun.

Perl 6 Compiler

Pugs commit emails

If you have ever been foolish enough to want an email for every commit in Pugs, Sam Vilain created a way to help you sip from the firehose. Have fun.

given when nested

Luke Palmer had a question about how nested when statements in a given block should act. His intuition disagreed with Pugs, but most others supported Pugs.

I don’t need to walk around in circles

Autrijus has made Pugs into a registered compiler for Parrot. Because Pugs already allowed you to embed Parrot code (PIR anyway) directly into Perl 6, this allows you to embed the Perl 6 in your PIR in your Perl 6. Now the possibilities are endless, at least until you blow your mental stack. Those of you with tail call optimization in your mental stack may simply go into an infinite loop if you prefer.

xor on lists

Trewth Seeker expressed his opinion about the proper definition of xor quite strongly. Unfortunately, his opinion is at odds with established mathematics, as Mark Biggar pointed out to him.

PGE features update

Patrick provided an update on the state of the Perl Grammar Engine. It has many nifty new features.

Pugs on Cygwin

Rob Kinyon and Gaal Yahas worked to improve Pugs support for Cygwin. Unfortunately the thread winds down with an unanswered question. Fortunately Stevan clued me in on IRC that things are not working just yet.

Pugs gets some objects and some rules

Autrijus announced that Pugs now has basic support for Objects and Rules. Sometimes he scares me, though usually he just makes me really want to learn Haskell.

regression test

Miroslav Silovic provided a regression test for hyper ops. Some people just don’t appreciate the fun of regressing.

basic test for classes

Stevan Little provided a patch for a simple object test. Autrijus applied it. That’s odd, because I am pretty sure that Stevan has the commit bit…

torturing PGE

Juerd provided a link to a big rule that could segfault PGE. It kind reminds me of a homework assignment I had to create a regular expression which matched all strings of numbers that did not contain any repeated digits. That’s easy in Perl, but hard in math. I think the resultant regex was somewhere around 17 MB.

Pugs 6.2.3 with Live CD

Autrijus released Pugs 6.2.3 which contains 10% more awesome then Pugs 6.2.2. You should check it out on the live CD that Ingo Blechschmidt released.

PXPerl meets Pugs

Grégoire Péan announced that he has added Pugs binaries to his windows distribution of Perl. Pretty cool. Autrijus innocently asked him to take on the slightly larger task of producing binaries of Parrot too, so that Pugs could be at its most powerful.


Wow, did you see how I mentioned Parrot before going into this new section. That was an awesome transition! My high school English teachers would be so proud.

character classes

Patrick wants character class opcodes of the form find first and find first not. Leo pointed him to some hysterical raisins who might help.

PGE on MinGW

François Perrad fixed a problem with building PGE on MinGW. Patrick applied the patch.

PIO_fdopen return value

Luke Palmer both intoduced me to the wonderfully cute phrase “untodid” and provided a patch making PIO_fdopen return NULL when given bad flags. Leo applied the patch, but Melvin Smith warned that this might be a bad idea. Silence followed.

embedding initialization

Jeff Horwitz was having trouble embedding PIR into C. Leo provided some pointers. Jeff was happy.

Test::Builder updates

Previously, Michael G Schwern announced an update to Test::Builder. chromatic asked if it was worth the upgrade. Michael replied probably, but I don’t think anyone has acted on it.


Robert Spier created a miniparrot at Bernhard Schmalhofer’s request. This miniparrot does not replace our make system, but it does make our website less camel centric.

Autrijus gets the commit bit

Leo, Autrijus, and Chip had one of the nerdiest conversations ever. The summary of which is that Autrijus gets commit priveledges for Parrot. The general consensus was that he was too productive in Haskell and we needed to hobble him with a real man’s language like C.

Parrot 0.2.0 “NLnet”

Leo announed the release of Parrot 0.2.0. This one didn’t seem to make it to Slashdot. That’s kinda sad, because I always get a warm feeling when I know about stuff before /. Oddly, Google Groups seems to have lost the email.

really make realclean

make realclean failed to find a few files: a flaw forcefully fixed by Jerry Gay.

load_bytecode shouldn’t segfault

Bob Rogers made it not. Leo applied the patch.

tell me sweet little lies

Patrick put out a request for a rudimentary set of lies and damn lies. People are welcome to provide benchmarks too.

Parrot Panic

Leo found that Parrot was panicking during start up. He rolled that patch back.

make testr

Leo put out a request for a make test target which would invoke Parrot twice, once to compile to PBC and once to run it. Dino Morelli provided a patch. Leo applied it.

trans test failures

Jens Rieks opened a ticket for some failing test long ago. Now he wondered if there was a status update. Warnock applies. update

Leo noticed that needed a little loving. Robert Spier provided it. He also mentioned that people could provide their own patches for it against . Now is your chance to contribute to Parrot’s public face.

runtime/parrot/library search

Jonathan Scott Duff wondered why runtime/parrot/library wasn’t in Parrot’s search paths. Leo added it for load_bytecode.

on the road to a tiny Parrot

Leo began down the road to miniparrot, creating first a Parrot without a config and using that to generate a config.fpmc for Parrot. The information provided there helps to create a larger Parrot.

MMD pmcs

Bob Rogers posted some questions about how to work with multi subs and provided a preliminary patch. Leo provided some answers but felt the need to pin down the calling conventions before the patch.

commit bit for Matt

Matt Diephouse received a commit bit. Congrats. Leo took the opportunity to remind himself to run make test before committing.

NULL deref in real_exception

Nicholas Clark found a NULL reference in real_exception. Leo explained that he needed to call Parrot_run_native to allocate the exception structute (and set the stack top pointer). Nicholas didn’t want to set the stack top as he was tracking some Perl refcount bugs.


Autrijus provided a patch to make PGE escape strings as Haskell FFI expects. Patrick suggested a slightly different approach, which Autrijus took.

Bug in Boolean.pmc

John Lenz found and fixed a bug in Boolean.pmc. Leo applied the patch and Juergen Boemmels provided a test.

svn revision number for releases

Andy Dougherty noticed that printed “failed” for release tarballs as they don’t have .svn directories. He changed it to print “done”. Leo applied the patch.

spawnw @args

Jeff Horwitz provided a patch which allows spawnw to take an array. Leo applied it (with a brief reminder on platform-specific ettiquette).

dynclasses build problem on Win32

Jerry Gay fixed a problem building dynclasses on Win32. Leo applied the patch.

basic JIT questions

Millsa Erlas had a few basic questions about Parrot’s JIT. Leo provided answers.

@ANON tests and test fixes

Jerry Gay fixed some tests and added some more. Leo applied the patch.

filepath manipulations

Leo put out a request for some filepath and string manipulation support in Parrot.

call syntax abstraction

In a failed attempt to dewarnock himself, Leo reported his call syntax abstraction proposal.

Old Tags

Nick Glencros suggested renaming (or possibly removing) some old tag files from our CVS days. Leo was unsure about the removing option but liked the renaming one.

MinGW build problems

François Perrad provided a patch to fix some build problems on MinGW. Leo applied the patch.

omniscient debugging in parrot

Andy Bach wondered how much of Omniscient Debugging would be possibly in Parrot. Leo reasoned that someone could add it with some work. It would involve replacing all mutating vtables with special versions that store extra information to allow them to roll back.

embedding/extending interface

Jeff Horwitz wondered who else was actively working on mebedding Parrot. Nicholas Clark provided a very uncertain pointer.

OO support in Parrot

Autrijus explained that Parrot’s current implementation made attribute access difficult. Leo went further saying that he felt it was wrong. The consensus is that Parrot needs to allow non-absolute access to attributes, so Leo made it so.

config.t fails

François Perrad found that config.t fails without first doing a make clean. Leo deemed his initial solution a little too quick and too dirty.

find ops return for not found

Patrick provided a patch which changes the return value of find and find_not to the string’s length (instead of -1) if the character does not occur. Warnock applies.

clean *_config files

Jerry Gay provided a patch to clean the _config files during make clean. Leo applied it.

MMD for logical ops

Leo changed the logical ops to return one of their operands as appropriate.

warning cleanup

Jerry Gay provided a patch to remove a warning on Win32. Bernhard Schmalhofer applied it.

Namespace updates?

Tim Bunce wondered whether any resolution with respect to namespaces had come about. Leo told him not much.

rules questions

Dino Morelli was trying to add some unit tests when he ran into questions. Patrick provided some answers but suggested further conversation move to p6l, which it did.

MD5 library clean ups and speed ups

Nick Glencross posted some updates to the MD5 library. This led to a few rounds of speading it up and comparing its speed with various other MD5 libraries. The final result is: slower than C but MUCH faster than pure Perl.

disassemble segfaults

Bob Rogers pointed out that disassemble was sefaulting on some byte code. Leo fixed it.

s/internal (exception)/real \1/

Jerry Gay provided a patch which changed some internal exceptions to real ones. Leo applied it.

failing tests

Tim Bunce reported some failing tests on Mac OS X. Leo fixed them.

small typo in PBC_COMPAT

Uwe Voelker provided a patch fixing a typo in PBC_COMPAT, which chromatic applied. He also noticed that p6rules/*.t did not have plans. Patrick welcomes all updates to PGE tests.


Dino Morelli added some tests for p6rules. Patrick applied the patch.

index up bug in PGE

Jerry Gay found a bug in PGE involving escaping sequences strangely. Leo tracked it down, and Patrick fixed it.

Parrot on Python

Kevin Tew wondered what the state of Python on Parrot was. Sam Ruby and Michal Wallace provided updates. Hopefully it will take off again soon.

paths with spaces need quoting

Ron Blaschke provided a patch to quote some paths that needed it in dynclasses. chromatic wondered if that would break with paths that already contain quotes.


Juergen Boemmels noticed that the SVN repository still contains some .cvsignore files. He suggested removing them, but a few things need to be updated to the svn world before that can happen. Bernhard Schmalhofer made it happen.

NULL pointer deref

Adrian Taylor found a NULL pointer problem in Parrot. Leo fixed it.

Parrot embedded in XSLT 2.0

Colin Paul Adams wondered how he could get information back from an embedded parrot. Autrijus pointed him to Parrot_call_sub with a signature of SS (takes a string and returns a string).

thread detatch hangs on win32

Jerry Gay noticed that thread detatch was hanging on Win32. He provided a patch to skip it so that other tests could fail in its place. Leo applied the patch.

Perl 6 Language

Semantics of Coroutines

Joshua Gatcomb wondered whether coroutines were invokable with new arguments on successive invocations. Some pointed out that allowing the arguments to change is a more powerful model, but I didn’t see anything definitive.

function composition operator

Michele Dondi wondered if there was a function composition binary operator. While one does not exist, it’s addable (as Ingo Blechschmidt demonstrated much later).

initialization of state vars

Ingo Blechschmidt wondered how state vars and parentheses would interact. Larry replied that his examples were probably correct.

==> automap?

Brad Bowman wondered if a single arg sub or block would automatically map when used on the sharp side of a pipe. Luke Palmer thought this might be too much dwimmery.

refactoring IDE

J Matisse Enzer wondered if Perl 6 would have strong IDE tools like refactoring supported or automated syntax completion. Larry explained that he would like to make it possible for Perl 6 to support these things “just as Perl 1 built in all the system interfaces”.

reduce precedence

Juerd wondered what the precedence for the reduce metaoperator was. Luke Palmer said “listop”.

piping into random things

Juerd wondered about piping into various things such as arrays, scalars, hashes, and filehandles. Larry gave one of his characteristically speculative answers.

That’s why they call me Mister Bitterness

Juerd wondered what “complain bitterly” meant in the context of the yada operator. Larry explained that ... would fail, ??? would warn, and !!! would die.

isa specifics

Stevan Little wondered how isa would act when called with junctions, nothing, classes, or instances. Larry explained that it would act intelligently by autothreading, returning a list of all options, returning a bool, or something I didn’t follow.

available operators

Juerd created a somewhat lengthy list of available operators, hoping to inspire someone to come up with a good operator for block labels. This led to a very meandering thread.

reduce meta operator

Some of you might be confused by my earlier meantion of a reduce metaoperator. Larry introduced one. Much debate ensued, but Larry seems fairly set on it.

override built ins

Andrew Savige wondered if he would be able to redefine built in functions such as read in Perl 6. Larry explained that Perl 6 will give you so much rope that you could hang yourself from several trees while blowing off your own foot with it.

opening stdout

Gaal Yahas wondered how to open stdout or a file named “-”. Larry explained that io() would have the dwimmy parts like opening stdout, while open would not try and dwim.

adverbial blocks explained

Terrence Brannon stumbled upon the phrase “adverbial blocks” but didn’t understand what it meant. Luke Palmer provided a very clear and cogent explanation.

circular dereferencing

Autrijus noticed that the autodereferencing of references would cause an infinite loop for circular refernce. Larry recanted and decided that the full on autodrill down was not as cool as he had initially thought, but he did warn us that next week he might think it was even cooler.

scoping of $/

Ingo Blechschmidt wondered what sort of scope $/ would have. Luke Palmer replied that it would be lexical just like Perl 5. Larry corrected him pointing out that it would actually be lexical, unlike Perl 5.

binding subs’ return values

Joshua Gatcomb wondered what binding of subs’ return values would do by default. Juerd answered that it would allow modification only for subs declared as lvalues.

use fatal, no fatal, exceptions, and undef

Aaron Sherman wondered how various scopes fatality levels would interact. Luke Palmer explained that you need to do 360s on the control pad while holding block. He also provided some thorough examples.

XML grammar in Perl 6

A while back Juerd wrote a Perl 5 script to transform the EBNF spec of XML into Perl 6 rules. Now that Pugs might be able to support it, he suggests that it would be a good project for a brave soul. No takers have yet appeared.

mailing list indexing

Aaron Sherman posted a link to his initial version of an annotated version of the mailing list. He asked for comments, but Warnock applies.

prefix adverbs

Someone who posted to Google Groups (receiving the unfortunate name mangling of asked if it made sense to write $a = stuff @foo, how => 'scrambled', 1, 2, 3; as $a = :>how('scrambled') stuff @foo, 1, 2, 3; or some such. Sadly, we will never know.

semantics of split

Autrijus asked if he had Pugs splitting correctly. It wasn’t, but it is now.

S29: punt

Rod Adams announced that he found the real world intruding too much and was going to have to leave off his work on S29. Sam Vilain, Aaron Sherman, and Max Maischein all volunteered to take up the effort.


Joshua Gatcomb wondered exactly what is chomped did. Larry Wall explained exactly what is chomped does.

character classes

Patrick, based on his experience with PGE, suggested a slightly new syntax for character classes in Perl 6. Larry liked the syntax and went on to muse about other unresolved issues involving character classes.

Numification of match objects

Autrijus noticed that numification of match objects made strings of digits numify to 1 (i.e., true). He didn’t like this. Actually no one did, so it has changed to numify as one would expect. After all, it can numify to 0 but true.

traits and properties API

Stéphane Payrard wondered when and how traits would interact with properties. Brent “Dax” Royal-Gordon and Larry provided answers.

single element lists

Jonathan Scott Duff wondered what (1)[0] would do. Larry though that we would have to specialize ()[] to parse as (,)[].

Void type?

Thomas Sandlaß, Rod Adams, and Autrijus speculated about ways to deal with a Void type. Nothing definitive came out of it though.

uniquely identifying objects

Stevan Little wondered if there was a way to uniquely identify objects in Perl 6. Larry pointed him to the .id and the associated =:= operator.

BEGIN and lexicals

Benjamin Smith wondered if BEGIN could modify lexicals that don’t really exist yet. Larry expressed the opinion that one should be able to modify compiler state in BEGIN blocks; however, he did not answer the question of what Benjamin’s example does.

:: vs ::: in rules

Patrick confused many people when he asked about the difference between :: and ::: at the top level of rules. The answer seems to be that ::: will fail the entire match while :: will simply fail it at that offset in the string on which it is attempting to match.

negatives of junctions

Larry noticed that != and !~ will confuse English speakers when applied to junctions. Luke noticed that defining $a != $b as !( $a == $b ) works, averting tragedy.

boxed types from builtins

Aaron Sherman worried that many built in functions return boxed types which could cause a big speed hit. Rod Adams explained that this was necessary but optimizations would be made available.


Juerd suggested using ./method to mean $?SELF.method (in an attempt to solve the long standing debate of $?SELF.method vs $_.method). Much discussion ensued although the general response seems favorable.

operators everywhere

Rob Kinyon noted that there seemed to be an extremely large number of operators. He expressed concern, because he had believed that P6 was going to have a small core with modules. Larry explained that most of these operators were the combination of a small set of operators and meta operators in a combinatorially explosive way, giving the wonderfully lucid example of [>>+^=<<]. Much discussion ensued.

BUILD and submethods

Ingo Blechschmidt wanted to be sure that all appropriate submethods would be called when they should and that only the correct one would be called when they shouldn’t all be. Larry answered that it did work as he expected.

$. vs $:

Luke Palmer was having trouble understanding the difference between $. and $:. Aaron Sherman prointed out a few differences according to A12.

not 4,3,2,1,0;

Autrijus wondered what the signature for not was in Perl 6. Larry explained that unlike Perl 5, Perl 6’s not function should act like !<<[4,3,2,1,0].

multiple colons in MMD

Luke Palmer caught Autrijus off guard when he pointed out that multis could have multiple levels of :, each of which is less important than the last. Larry surmised that they might not have documented this hard enough.

Nested Captures

Carl Franks started a very long thread when he noted that nested captures caused extra layers in the match array rather than counting parens like Perl 5. This led to discussion of 0 vs 1 indexing. Discussion ensued, with the resulting decision that $0 == $/[0]. There was much rejoicing.

'1.28' * '2.56'

Autrijus wondered what path '1.28' * '2.56' should take to arrive at 3.2768. Larry told him that infix * used prefix + to numify non-Num args.

methods from roles vs classes

Aaron Sherman wants to lazily load a role but only the first time it is necessary. Luke Palmer assured him that his example would work correctly.

currying and defaults

Aaron Sherman, in his efforts to get up to speed on S29, wondered how currying would interact with default values. Larry explained that default values would not be bound until the invocation of the curried function.

precedence of custom infix ops

Ingo Blechschmidt wondered how to define the precedence of custon infix ops. Luke Palmer pointed out the looser, tighter, and equiv traits (by default it is equiv( &infix:<+> ) ).

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