This Week in Perl 6, April 26 - May 3, 2005


Welcome to another week’s summary. This week I shall endeavor not to delete my summary accidentally or destroy the world. Here we go with p6c.

Perl 6 Compilers

Implicit $_ on for Loops

Kiran Kumar found a bug in Pugs involving for loops which use $_ but don’t iterate over it. Aaron Sherman and Luke Palmer confirmed the bug. There’s no word as to its final status, but given the rate of development of Pugs…

Pugs Darcs Trouble

Glenn Ehrlich noticed that Pugs’ Darcs repository wasn’t updating. Sam Vilain explained that occasionally a daemon needed kicking.

Memory Game v0.2

BÁRTHÁZI András announced the release of the latest version of Memory. He also put out a call for 85x75 pixel photos for the next version.

Haddock for Pugs

Stuart Cook decided that the easiest way for him to understand Pugs internals was to provide better documentation. To that end he started working with Haddock to automatically generate cross-linked documentation for Pugs. He even met with some success.

is export Trait

Garrett Rooney wondered why the is export trait appeared to do nothing in Pugs. Stevan Little explained that it was just a place holder which, though it parses, does nothing semantically yet.

Pugs 6.2.2

Autrijus proudly announced the release of Pugs 6.2.2. It features many, many changes. High on the list is a bunch of speed ups, and also thread-safe, deadlock-free internal storage.

Pugs on Cygwin

Rob Kinyon noticed that Pugs had trouble on Cygwin. He has made some headway rectifying the situation, although work remains to be done.

Pugs TODO Model

Stevan has put some more thought into the TODO model for Pugs. His latest suggestion, annotating TODO tests with a flag indicating why they are not passing, seems a little less hackish then the last one and received general support.

Parrot Hiding Inside Pugs

Autrijus wanted to embed the newly released PGE, which is PIR code that runs on Parrot. He decided to embed Parrot into Pugs. He also posted an interesting link to JHC as a possible bootstrap solution.

New PGE Released

Maybe I should have mentioned this first. Patrick R. Michaud released a new version of the Parrot Grammar Engine. It is entirely PIR code and generates PIR code. It has many features but not enough tests… <cough>hint</cough>.


Monthly Release?

Jared Rhine wondered if the monthly releases included April. Chip announced that April’s release would be slushier then most, but would start on the fourth.

t/op/debuginfo.t Failure

François Perrad noticed a failure in debuginfo. Leo pointed out that it was an issue of flushing output handles. Francois provided a patch (well, actually two patches). Warnock applies to the second.

ParTcl Happy?

Will Coleda thought that ParTcl’s GC bugs had finally gone away. Leo burst his bubble. Apparently these GC bugs can disappear and reappear according to sunspot activity.

S1zzegfault in load_bytecode

Nick Glencross submitted a patch fixing a segfault in load_bytecode. Jens pointed out that it should use real_exception instead of internal_exception. chromatic offered to write the test. There is no official committed message though.

Large PackFile Tinker

Leo implemented a change in the interpreter PackFile structure which has been under discussion for a long time. Unfortunately, it has the potential to break a lot of JIT stuff. Tests and fixes would be wonderful.

PMC Inheritance Issue

Nicholas Clark had some trouble with his Perl5 PMCs. Later, he posted a “mea culpa” email, but Leo provided some useful pointers anyway.

RT Cleanup

Bernhard Schmalhofer cleaned out an old ticket from RT.

RFC assign Px, Py

Some time ago, Leo requested comments on the semantics of assign. Brent “Dax” Royal-Gordon tried to de-Warnock the thread with his support. He also suggested a clone operator.

NULL in real_exception

Nicholas Clark struggled with a NULL pointer deref in real_exception. Leo pointed him toward the correct approach.

Unary Operator Overhaul

Having finished overhauling the infix operators, Leo set to work updating the unary operators to provide variants which allocate their results.

Die die, die!

Leo announced that he was removing the die opcode and adding a Bruce Willis opcode in its place. Unlike Mr. Willis, the die_hard opcode actually died relatively easily. Leo then renamed it to just die out of popular demand.

Core Dump with Computed goto Core

Nick Glencross found a core dump with the computed goto core. Leo explained that a hackish attempted optimization caused it. He also fixed it.

Ignore Generated Files in SVN

Juergen Boemmels made SVN ignore some .so files. Leo asked if it could also ignore .rej and .orig files.


Nicholas Clark found that DYNSUPER did not work well with his dynamic classes. Leo provided a suggestion for something to try and also suggested a super vtable call.

MMD Type Info

Autrijus wondered how Parrot carries around the type info for MMD. Leo provided answers.


Markus Amslser wrote a tiny webserver in IMC. This led to the discovery of that the binary to ASCII transcoding is missing. Leo suggested several possible solutions.

Ponie’s Use of PMC Flag Bits

Nicholas Clark asked how best to use the 8 private bits of PMC in Ponie. His initial thought was to mark type with it. Leo suggested that adding the type to the flag bits was unnecessary, as one can usually just call a vtable or MMD function directly and the type will work out.

Built-in MMDs as Methods

Leo added support for calling built-in MMDs on objects as methods.

Unary and Infix Ops Update

Leo posted a summary and TODO for his overhaul of opcodes that return new results. Jerry Gay and Bob Rogers helped fill out the corners. Bob even provided some tests.

Parrot and Ref Counting

Robin Redeker wondered why Parrot had decided to go with a non-ref counting GC. Dan Sugalski took responsibility for the decision and explained his motivations. Non-ref counting GCs are essentially simpler, cleaner, and faster. You can get a more detailed answer from reading the thread or Dan’s Squawks of the Parrot: What the heck is: Garbage Collection from way back when.

Deprecate fast_call?

Leo mused that he would like to deprecate the fast_call PIR construct. No one squawked, so I call it officially deprecated.

Win32 Thread Primitives

Vladimir Lipsky and Leo went back and forth a few times working out thread primitives for Windows. I am not sure what state they finally reached.

Call Syntax Abstraction

Leo posted a proposal for a calling convention abstraction. No comments have appeared yet, but it has not been up for long.

Tailcalls in PIR

Patrick R. Michaud wondered if PIR supported tailcalls and tailmethods yet. Leo provided a few pointers. Bob Rogers suggested a nice syntax, which Leo implemented.

Vtables in extend.h

Nicholas Clark noted a need for vtables in extend.h. Leo agreed that they should be auto-generated. chromatic eagerly requested the chance to write the Perl code that does this auto-generation.


Michael G. Schwern announced that he’d removed BAILOUT from Test::Builder in favor of BAIL_OUT. He admitted that a deprecated BAILOUT would remain as undocumented. At some point we should update.

Perl 6 Language

Anonymous Roles and Closures

Aaron Sherman wondered if he could generate anonymous roles that are also closures. It made my head hurt. People seem to think it’s possible though.

Peter Piper picked a hash…

Ingo Blechschmidt wondered what pick would return when called on a hash. Rod Adams suggested that it would return a pair. Larry thought that would be a good idea, if perhaps difficult to implement.

All (Junctions, Bad Subjects, Indecision)

Joshua Gatcomb found that he could use junctions to quickly answer questions but not provide specifics. Sadly, he is not the first person to have this problem. Junctions naturally provide Boolean operations but do not naturally explain what motivated that answer. Perhaps they should be thrown out along with the axiom of choice. After all, do we really need a basis for ALL of our vector spaces?

is rw a No-Op on References?

Ingo Blechschmidt wondered if is rw did anything for references, as you can still modify the value to which they refer. Juerd answered basically yes.

Complex Number Package

Jonathan Lang wondered about creating a complex number package. Including returning junctions of values for roots of unity. Unfortunately these lists can be quite large, even infinite. Thus, he wondered if he could use lazy junctions. Thomas Sandlaß conjectured that he could by the “law of laziness preservation”.

Auto-Threading of Junctions and Threads

Aaron Sherman worried that the auto-threading of junction would actually run in separate threads. This is most assuredly not the common case, although some warped soul could implement it that way.

Context of Indices

Autrijus asked what context want would provide when used as an index. Larry provided answers.

Sun’s Fortress

Autrijus posted a link to a next-generation computer language from Sun called Fortress and then went on to ask about parameterized types, tuple types, and block labels. Bad Autrijus! Make summarizers lives hard. Then we have to punt like this rather than try to extract the three different threads at once.

Restricting Variable Scopes With while

Joshua Gatcomb wanted to know how he could restrict the scope of variables used in the conditionals of his while statement to the loop. This led to some discussion about the implementation of while as a macro or some other beast. Larry began to ponder the submacro.

FIRST, LAST et al. Support in Pugs

David Christensen decided to try to add support for FIRST, LAST blocks and the like into Pugs. This led him to p6l with some questions about traits which are closures. Answers and suggestions followed.

Junctions of Classes

Ingo Blechschmidt wondered how junctions of classes would act. The consensus seems to be that they act as type specifiers of a sort, restricting whatever the variables they describe can contain.

Subtype Declarations

Luke Palmer wondered what exactly subtype declarations provided and suggested jettisoning them. Larry remained unconvinced.

Labels on Blocks

Stevan Little wondered if there was some way to attach labels to blocks. Discussion ensued, including a comment from Larry that it won’t need to be redone.

open and pipe

Gaal Yahas proposed a basic open and pipe built-in for discussion. Discussion followed. Larry mentioned that he has “pretty much” blessed io (from IO::All).

Is if Function?

Juerd wondered if if as a function had unintended consequences. Fortunately, if is not a function, it is a statement-level construct.

Junctions in use Statements

Juerd wondered if he could say use strict & warnings. Larry explained that there were parsing problems with it and possibly limited utility, but he has not officially ruled it out, as the problems have workarounds.

.foo() == one($, $?

This great quandary continues. This week, Larry is leaning towards the .foo() == $ camp, but nothing is yet set. He also suggested $^ as being equivalent to $?SELF (which I really like). Time will tell how this one will work out. My prediction is that the argument will rage on until Pugs is ready to implement it and needs a definitive answer…then it will change a few more times.

Type System Questions

Autrijus asked a few questions about the type system, and at which times it did what things. Larry provided some answers.

Posting via the Google Groups interface does not work. To post to any of these mailing lists please subscribe by sending email to,, or If you find these summaries useful or enjoyable, please consider contributing to the Perl Foundation to help support the development of Perl. You might also like to send feedback to



Something wrong with this article? Help us out by opening an issue or pull request on GitHub