Weekly Perl 6 mailing list summary for 21-28 January, 2007

  This week on the Perl 6 mailing lists

     "Take the longest token, lie down and if the unease persists, write
     some code..."

     -- Brad Bowman, in 'DFA/NFA context is non-local <http://xrl.us/uqix>'


  perl6-language

   RAII in Perl6/Parrot <http://xrl.us/tz2r>

     Previously on this thread, Blair Sutton asked if Perl 6 would be able
     to do RAII. He cited some articles which expressed the view that it
     was not possible in Python due to the fact that garbage collection
     does not offer deterministic finalization. This led to the question of
     whether Perl 6 would suffer from the same problem due to Parrot's
     style of garbage collection.

     Larry Wall replied that deterministic reference counting was only one
     way to provide transactional security and timely destruction. He
     assured Blair that Perl 6 has ways to let you not care about some
     dependencies, while paying attention to others.

     Blair appreciated Larry's explanation, and admitted to relying on the
     deterministic nature of C++, and using RAII to manage locks between
     threads and tear apart sockets cleanly. He asked for an example of
     Perl 6 offering the capability to execute code once every reference to
     an object has been removed. Luke Palmer replied that the LEAVE closure
     trait was a general method for addressing this.

     This week, Blair posted a script in Perl 5 with a multi-threaded RAII
     idiom. Blair asked if the LEAVE closure trait takes the previous role
     of P5's DESTROY or if it will always be executed when one falls out of
     scope.

   Numeric Semantics <http://xrl.us/t3o7>

     Last week, the subthread was further expanded, with TSa suggesting
     that all rounding functions such as floor, round and trunc take an
     optional second argument which defines the jump size. TSa also
     proposed a number of division function pairs, such as fdiv and fmod
     for flooring division and modulus, or tdiv and tmod for truncating
     division and modulus. Smylers felt that this would introduce far too
     many functions in to the Perl core, given that few people would use
     them. Smylers felt that it was more appropriate to have them as
     modules. Jonathan Lang added that it was unlikely anyone would need
     multiple definitions of division and modulus at any given time, so
     modules made sense. The only question he saw was which definition was
     default, the mathematically elegant one or the industry standard one.

     The main thread was revived when TSa replied to Luke Palmer's question
     of whether 1 is different from 1.0. TSa wanted 1 to be an Int and 1.0
     to be a Num. There was some discussion with Jonathan Lang over the
     relationship between Int and Num, specifically which one does the
     other.

     This week, Larry Wall put his foot down and stated that the default
     `/` operator is not going to do integer division and that this is not
     negotiable. Later in the thread, Larry said that for various practical
     reasons, he didn't think that Int can be treated as a subset of Num.
     He agreed that `1.0 == 1 !=== 1.0`.

     Larry's messages generated praise from Smylers, but TSa was not
     satisfied. However, he did not receive a noteworthy response this
     week.

   [svn:perl6-synopsis] r13523 - doc/trunk/design/syn <http://xrl.us/uqim>

     This commit message by Larry Wall logged the following: "Tweak `|` to
     provide longest-token instead of short-circuit semantics. Now use `||`
     for old short-circuit semantics!" In a follow-up message, Larry
     elaborated:

     This checking majorly changes the semantics of `|` within regex to
     support required longest-token matching semantics rather than
     left-to-right matching. It will enable us to write parsers more
     consistently, and it also opens up normal regexes to better
     optimization via tries and such. You can now use `||` for the old `|`
     semantics, which is majorly consistent with how `|` and `||` work
     outside of regexen.

     Patrick Michaud asked if a similar situation would arise for `&`
     versus `&&`. Larry answered that, for reasons of consistency, that
     would indeed be the case.

   The S13 "is commutative" trait <http://xrl.us/uqin>

     After reading that binary operators may be declared as commutative,
     Dave Whipp asked if this is restricted to only binary operators, or if
     he could tag any function/method with the trait. After a brief
     discussion, Larry replied that he had decided "is commutative" must
     die of ill-definedness. See instead the recent S13 change to support
     multiple signatures on a single body.

   [svn:perl6-synopsis] r13529 - doc/trunk/design/syn <http://xrl.us/uqit>

     This commit, by Larry Wall, changes how regular expressions are
     analyzed. They are seen as pattern/action pairs and grammars as
     collections of those pairs. In addition 'token' is defined more
     rigorously.

   Remember: Outlaw to declare a lexical twice in the same scope
   <http://xrl.us/uqiu>

     Steve Lukas reminded people of a proposal from September which
     involved a change on S04 and linked to an earlier edition of this
     summary to describe the conclusions which had been reached. He
     requested that the changes be made. Carl Mäsak added that he also
     considered this to be an important issue. He wanted to see a warning
     when a lexical is declared twice in the same scope.

     Dave Mitchell and Smylers clarified how it works in Perl 5 (it's
     possible, but generates a warning).

   DFA/NFA context is non-local <http://xrl.us/uqix>

     Brad Bowman expressed his concern about the context dependence of DFA
     prefix mode. He felt this might be because he hadn't yet digested the
     new rules completely.

   Smooth or Chunky? <http://xrl.us/uqi7>

     Larry Wall asked for some advice with a missing generalization that he
     hadn't been able to work out yet. Given that `zip` and `each` produce
     similar results, he wondered what is the use of two functions which do
     almost the same thing. This led him to believe that zip should return
     something different and let the context determine whether the result
     should be flattened. This led to musings on a default smooth and an
     optional chunky, and a question on whether chunky should be the
     default when it makes more sense. He suggested various options.

     Darren Duncan thought that the Perl 5 approach of default 'smooth'
     with optional 'chunking' was appropriate. As an example he offered the
     smooth `map { $_, $_ * 10 }, 1..3` versus `map {[$_, $_ * 10]}, 1..3`.
     Larry replied that this was one function where the approach was
     possible, but that Perl 5 has many places where it fails to scale well
     to a multi-programmer team.

     Ruud H.G. van Tol believed that it looked like a 'multiple faces'
     domain. He sees the dimensionally structured data as a living entity
     which should give different representations depending upon the
     requirements. As an example, he cited a meal, a recipe and a shopping
     list, adding that his preference was for the shopping list to be
     ordered by where things are found in the store. Brad Bowman suggested
     that the dimensional information should be retained, but that it might
     not need to be returned.

     Ben Morrow proposed `[[]]` as a nice visual way to indicate that a
     list should be built. Blair Sutton listed several possible syntax
     options. Austin Frank joined in, offering the outverse of `[;]`,
     namely `];[`.

   Map on a multislice <http://xrl.us/uqja>

     Joe Gottman wanted to know if map on a multislice performs deep or
     shallow iteration. He wanted to know what the default iteration level
     was and how to override it. Dr. Ruud added that there's also the
     option of depth first or width first.

  perl6-internals

   [perl #41185] [BUG]: examples/shootout/regexdna.pir.input: Persistently
   failing test <http://xrl.us/t78e>

     Earlier, in ticket [perl #41185] <http://xrl.us/t78f>, James Keenan
     reported a problem with a failing test in `shootout.t` on Mac OSX.

     This week he reported that tests had passed for several weeks, but had
     recently started to fail again. He included the output of `make test`.
     As of February 6th, the test was still failing on Darwin.

   Re: [perl #41230] [BUG] t/codingstd/perlcritic.t uses too many resources
   <http://xrl.us/uqjc>

     Earlier, Jerry Gay complained that the perlcritic coding standards
     test was using resources, and asked in ticket [perl #41230]
     <http://xrl.us/t9n4> if someone could look in to this problem. Paul
     Cochrane reported that he thought there was a memory issue relating to
     `critique()` and that the memory was only freed up when the tests for
     a given policy are complete. Paul elaborated on what what he had
     attempted to address the issue.

     This week Jerry Gay congratulated Jeffrey Thalhammer on version 1.01
     of Perl::Critic, which solved the memory issue.

   [perl #41267] [TODO] rename 'clip' pdd directory to 'draft'
   <http://xrl.us/ucn6>

     In ticket [perl #41267] <http://xrl.us/ucom>, Jerry Gay announced that
     the `clip` directory had been renamed to `draft`.

   [perl #41280] [PDD] adding methods to subs as objects
   <http://xrl.us/uqjd>

     In ticket [perl #41280] <http://xrl.us/u2yx>, Allison Randal quoted
     Patrick Michaud from IRC. Patrick explained that Larry Wall's most
     recent change to S05 would require adding the ability to attach
     methods to subs.

   [perl #32667] [PATCH] IMCC - documentation needs updating
   <http://xrl.us/uqje>

     Bram Geron included a patch in ticket [perl #32667]
     <http://xrl.us/u2yy> which adds new syntax to `docs/imcc/syntax.pod`
     and fixes some typos. It also references where flags are explained. It
     was applied as r16678.

   More embedding questions <http://xrl.us/uqjf>

     Isaac Freeman explained that he needs an embedding interface which
     allows more control over the interpreter and cited some examples of
     control he required. He asked specifically about the ability to
     inspect and modify namespaces. chromatic pointed him to PDD 21, which
     is not completely implemented.

   repository open for commits <http://xrl.us/uqjg>

     Jerry Gay announced that the repository was now open for commits
     again, following the recent Parrot release.

   [perl #41287] [PATCH] fix 0.4.8 announcement on parrotcode.org
   <http://xrl.us/uqjh>

     Allison Randal created a ticket ([perl #41287] <http://xrl.us/u2yz>)
     with a patch to fix typos in the release announcement for 0.4.8. Will
     Coleda applied it.

   [perl #41291] [BUG} Can't use null PMC with :multi sub
   <http://xrl.us/uqji>

     In ticket [perl #41291] <http://xrl.us/u2y2>, Matt Diephouse included
     an example piece of code demonstrating the problem. Leopold Toetsch
     noted that a NULL PMC was never actually specced, but that he did
     consider it like a NULL pointer in C. He felt it was debatable whether
     the use Matt demonstrated should be allowed.

   [perl #41292] [PATCH] make languages/cola/{lexer,parser}.c comply with
   coding standards <http://xrl.us/uqjj>

     In ticket [perl #41292] <http://xrl.us/u2y3>, James Bence submitted a
     patch to make the test `t/codingstd/trailing_space.t` pass. He felt it
     would be best to make a utility program which would eliminate trailing
     spaces.

     Paul Cochrane asked which version of Parrot James was using, as the
     files involved should be marked as exempt because they are
     automatically generated. In r16702 the tests pass even without the
     patch.

   Tcl, trace, profiling... <http://xrl.us/uqjk>

     Will Coleda announced that he had two issues with the new Tcl
     implementation: speed and the implementation of `trace`. After noting
     that there is a way to set traces for Parrot subroutines, he requested
     the ability to declare hooks to call pre- and post sub invocations.
     Ideally these could be declared at compile time. He offered to write
     more complete specifications if the idea was interesting to others.

     Allison Randal offered a few comments and requested the detailed
     proposal. Jerry Gay advised looking at Perl 5's Hook::LexWrap.
     Klaas-Jan Stol offered a suggestion which would leave the original
     subroutine untouched.

   [perl #41293] [BUG]: t/compilers/tge/basic.t: Failed during 'make test'
   but passed with 'prove' <http://xrl.us/uqjm>

     James Keenan reported a failing `make test`. This was ticket [perl
     #41293] <http://xrl.us/u2y4>.

   How handle the next parameter of invoke method in a PMC ?
   <http://xrl.us/uqjp>

     François Perrad stated that in Lua, a metamethod `__call` is required.
     He included some code demonstrating what he would like to do, and
     noted that the code and some todo tests had been added.

   [perl #41310] [CAGE] autogenerated PMC stubs kill compile
   <http://xrl.us/uqjq>

     Allison Randal created ticket [perl #41310] <http://xrl.us/u2y5>. She
     reported that PMC stubs which are generated with
     `tools/dev/gen_class.pl` terminate the compilation the first time
     miniparrot is run because the new stub overrides the `namespace`
     method. She suggested ways in which this might be solved.

   [perl #41312] [TODO] - Docs - update FAQ <http://xrl.us/uqjs>

     In ticket [perl #41312] <http://xrl.us/u2y6>, Will Coleda pointed out
     several outdated facets of the FAQ and requested that they be fixed.

   [perl #41317] [PATCH] parrot component/interface stability
   classification <http://xrl.us/uqjv>

     In ticket [perl #41317] <http://xrl.us/u2y7>, Jerry Gay included a
     patch of a document classifying Parrot component and interface
     stability. He requested comments. Allison Randal approved of the
     document.

   [perl #41320] [PATCH] Added rename() method to os.pmc
   <http://xrl.us/uqjw>

     Ticket [perl #41320] <http://xrl.us/u2y8> contained Kay-Uwe Huell's
     patch with a `rename` function. It was applied as r16771.

   [perl #41323] [CAGE] convert C<theINTERP> to C<interp>
   <http://xrl.us/uqjx>

     Jerry Gay made a ticket ([perl #41323] <http://xrl.us/u2y9>) where he
     noted that any instances of `theINTERP` should be spelled as `interp`.
     Nuno Carvalho submitted a patch, which was applied as r16789. Jerry
     Gay was able to confirm that it worked for Win32 in addition to Linux.

   [perl #41324] [PATCH] Eliminate '//'-style comments <http://xrl.us/uqjy>

     Andy Dougherty submitted a patch to remove `//` comments, which were
     giving problems with his compiler. See ticket [perl #41324]
     <http://xrl.us/u2za> for more information.

   [perl #41325] [PATCH] Fill in missing pointer cast in
   <http://xrl.us/uqjz>

     Andy Dougherty submitted a patch to allow Parrot to compile on his old
     Sun C compiler. He put it in ticket [perl #41325]
     <http://xrl.us/u2zb>.

   [perl #41326] [PATCH] Work around an optimization bug in Sun's WorkShop
   Compilers 4.2 <http://xrl.us/uqj2>

     In ticket [perl #41326] <http://xrl.us/u2zc>, Andy Dougherty submitted
     a patch to work around an obscure bug in Sun's WorkShop Compilers 4.2.

   [perl #41328] [BUG] pmc2c generates unnecessary code for void functions
   <http://xrl.us/uqj3>

     Jerry Gay reported some warnings when compiling `src/pmc/pmethod.c` in
     ticket [perl #41328] <http://xrl.us/u2zd>. James Keenan explained the
     origin of the code in question, and advised moving the code to a
     branch until tests prove it suitable for trunk.

   [perl #41329] [BUG]: Imposition of coding standards breaks tests in
   t/tools/pmc2cutils/ <http://xrl.us/uqj4>

     James Keenan noted, in ticket [perl #41329] <http://xrl.us/u2ze>, that
     coding standards tests break some tests in `t/tools/pmc2cutils`. He
     believed that it happened in r16751, when code was changed to conform
     with the standards but wasn't run against the tests and submitted a
     patch to correct the problem. Paul Cochrane explained that he had run
     the tests, but that he hadn't done enough, and apologized.

   [perl #41331] Imposition of coding standards breaks tests in tcl.
   <http://xrl.us/uqj5>

     In ticket [perl #41331] <http://xrl.us/u2zf>, Will Coleda referenced
     an earlier thread ([perl #41329] [BUG]: Imposition of coding standards
     breaks tests in t/tools/pmc2cutils/ <http://xrl.us/uqj4>) which
     mentioned that some tests failed as a result of coding standards being
     applied. Several Tcl tests were failing. They were fixed by r16774.

   __init vs. __init_pmc <http://xrl.us/uqj6>

     Leopold Toetsch noted that some changes not too long before the
     release had broken `pg.t`. He found the problem in the object
     constructor, and mentioned that he'd made several attempts to unify
     object construction but that it wasn't very successful.

     Matt Diephouse explained that he had made the change with Allison
     Randal's approval, to eliminate differences between PMCs and objects.
     Leopold replied that he thought the differences were confusing but
     that they still were. He linked to his proposal for method calling
     <http://xrl.us/u2zg>.

   [PATCH] PIR language using PGE (2) <http://xrl.us/uqj7>

     Klaas-Jan Stol submitted a patch for PIR using PGE. Jerry Gay applied
     it (with minor changes) as of r16831.

   [perl #41353] [PATCH] Extended very limited PIO_unix_pipe() function in
   src/io/io_unix.c <http://xrl.us/uqj9>

     Kay-Uwe Huell created ticket [perl #41353] <http://xrl.us/u2zh>.
     Included was a patch to extend the `open` function.

  perl6-compiler

   Parrot 0.4.8 Released <http://xrl.us/uqka>

     Jerry Gay announced the release of Parrot 0.4.8, "Eponymous".

     Jarkko Hietaniemi questioned whether there was in fact extended
     support for Tru64, as he had only reported problems for subsystems
     like PGE. chromatic offered Jarkko commit access, but Jarkko declined.

     Matt Diephouse volunteered to work on Tru64 if someone could give him
     access to a system. Nicholas Clark replied that HP gave access to a
     number of test systems, but not Tru64. Jarkko grumbled about HP's
     restriction. Unfortunately he was not able to provide a developer with
     Tru64 access. He thought that perhaps development on any 64-bit
     platform would already improve Parrot.

  Acknowledgements

     This summary was prepared using Mail::Summary::Tools
     <http://xrl.us/qvno>, available on CPAN.

     If you appreciate Perl, consider contributing to the Perl Foundation
     <http://donate.perlfoundation.org> to help support the development of
     Perl.

     Thank you to everyone who has pointed out mistakes and offered
     suggestions for improving this series. Comments on this summary can be
     sent to Ann Barcomb, <[email protected]>.

  Distribution

     This summary can be found in the following places:

     * use.perl.org <http://use.perl.org/>
     * The Pugs blog <http://pugs.blogs.com/>
     * The perl6-announce mailing list <http://xrl.us/qycj>
     * ONLamp <http://www.oreillynet.com/onlamp/blog/>

  See Also

     * Perl Foundation activities <http://blog.perlfoundation.org>
     * Perl 6 Development <http://dev.perl.org/perl6>
     * Planet Perl Six <http://planetsix.perlfoundation.org/>