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Perl 6 summary, 10-16 September, 2006

Journal written by kudra (4364) and posted by kudra on 2006.09.16 15:17   Printer-friendly
This week on the Perl 6 mailing lists

This summary has been posted early because I will be going to OSCON Europe on Sunday. Next week's summary will include any threads which were not included this week.


multi method dispatching of optional arguments

Last week, Mark Stosberg wanted the specifications to address what should happen in MMD when optional arguments are present (S12). He patched mmd-draft.txt and sent the text to the newsgroup. Luke Palmer offered a suggestion.

Ph. Marek wondered if there will be MMD based on the value of parameters, as in Haskell. Audrey Tang confirmed this and pointed to S06. Trey Harris updated it with a reference to S12. Ruud H.G. van Tol also offered an example of syntax.

This week, Larry Wall clarified further, noting that every scalar value is a one-element subset of its type.

Inf appears to be unspec'ed

Mark Stosberg was unable to find the formal definitions for Inf, not and true. Later he found them, and was able to add smart links.

Reduced assignment operator?

Audrey Tang noted that S03 was inconsistent about the treatment of assignment operators in the reduction operator. Audrey further commented that she doesn't see a problem with supporting assignment reductions as a syntactic exception. Larry Wall replied that it was worth supporting.

Outlaw to declare a lexical twice in the same scope

Steve Lukas quoted S04: "If you declare a lexical twice in the same scope, it is the same lexical." He felt that declaring the same lexical should give an error, because when he does this, he's made a mistake. Rick Delaney disagreed; for development or debugging he will often add a second declaration line to temporarily override the first. Juerd agreed with Steve. He appreciates that my $foo always gives a new variable, so he does not need to know anything about the surrounding code. Carl Mäsak also wanted the compiler to catch second declarations.

Naming the method form of s///

Earlier, Mark J. Reed noted that according to S05, the string method equivalent of
s/// is subst. He felt it might be easily confused with substr and suggested replace.

A long discussion on how the method would actually work followed.

Recently, Larry Wall noted that he should clarify the role of = with regard to preceding declarators. They control how often the expression is evaluated.

META vs meta

David Brunton noted that S12 specifies $obj.META, but in Pugs it is implemented as $obj.meta. He wanted to know if he could change meta to META. Larry Wall replied that he was considering renaming the method to use interrogative pronouns. David Green commented on Larry's proposed names, and Larry responded.

Sam Vilain wondered if upper case was needed. Jonathan Scott Duff thought that it fit in with Perl's culture. Aaron Sherman had some other suggestions for avoiding namespace pollution.

David Brunton wanted to know if there was some reason that the meta methods could not be part of a default function package. Aaron Sherman gave two reasons why this was not desirable.

single named param

Gaal Yahas wondered if :(:$x) was a single named parameter called $x or a default invocant and a single required positional named $x. Audrey Tang replied that a default invocant would not make sense because there is nothing to default to. Gaal then wondered what invocant is constructed for method foo ($just_a_named_param). Larry Wall replied, and Mark Stosberg also commented. Audrey answered too.

[svn:perl6-synopsis] r11965 - doc/trunk/design/syn

Larry Wall made a commit to S03, which led Ruud H.G. van Tol to ask if [=] $x, @y was equivalent to $x = @y[0] = @y[1] = @y[2] ... @y[-2] = y[-1]. Larry replied that they were. Ruud asked for additional clarification.

Unpacking tree node parameters

Earlier, Gaal Yahas asked for some clarification on the intent in S06's "Unpacking
tree node parameters" so that he could introduce the optional use of the
colon more gradually.

This week, Audrey Tang replied with answers to Gaal's questions.

[svn:perl6-synopsis] r11969 - doc/trunk/design/syn

Several threads grew from Larry Wall's commits on the X operator.

Darren Duncan expressed his appreciation for it. Miroslav Silovic asked if it would be possible to extend next to pass arguments to the 'nexted' iterator.

In thread [svn:perl6-synopsis] r11971 - doc/trunk/design/syn, Daniel Hulme requested a variant which does the diagonal order.

[svn:perl6-synopsis] r11975 - doc/trunk/design/syn led to additional comments. Carl Mäsak wanted to know why X-X is needed if X already concatenates strings. Daniel Hulme thought it was an incomplete change which should have read XX. Carl agreed, but thought X,X would be nicer.

assigning to named parameters

Aaron Sherman wondered if it would be possible to treat named parameters as lvalues, so that foo(:a<1>, :b<2>) could become foo(:a=1, :b=2).

-X file test operators

Aaron Sherman raised ambiguity issues between identifiers with dashes in their names, like the file test operators, and unary minus (-4). Juerd replied with proposals for phasing out -e and friends in favour of some more flexible/modern approaches. Larry Wall cleared up the syntax for calling prefix operators as methods, and other funny method names.

Acording to S05, due to the longest token rule -e will be parsed as the prefix op -e, and not as prefix unary minus and call to e. However, this is only the case if the prefix operator -e is actually defined.

A discussion on identifiers with funny characters in them also started under this thread.

Parrot Porters

JSON compiler

Will Coleda announced that he had added a JSON compiler with help from Jerry Gay and Nuno Carvalho.

[svn ci] apps/p3

Leopold Toetsch announced that he'd created a Parrot-based slide presentation program. He requested improvements and suggestions.

[perl #40316] [NEW] opcodes not tested script

Fonseka created ticket [perl #40316] to include a patch for a script which outputs the opcodes not covered by tests. Currently all but 7% of the opcodes are used in real tests.

The thread continued in Re: [perl #40316] [NEW] opcodes not tested script, after the code was committed as r14594. Leopold Toetsch commented on how disassemble was largely untested, and Fonseka replied.

[perl #40319] [PATCH] PGE test file written in PIR revisited

In ticket [perl #40319], Nuno Carvalho reported that he had cleaned t/compilers/pge/06-grammar.t and included a patch. Patrick R. Michaud noted that test 10 was marked 'todo' but passed, and wanted to know why it was marked 'todo'. Patrick applied it as r14606 and r14607.

The Interp structure

Alberto Simões has been trying to improve compilers/imcc to make it reentrant by removing globals and creating an object with the variables which is relevant to the parser. He noted that an Interp structure is being passed, but believes this does not duplicate the functionality he is creating, and asked for a confirmation.

Libraries, dynpmc and Visual C++

Ron Blaschke reported a fatal error when linking gdbmhash.dll on Windows XP with Visual C++. Will Coleda applied the patch as r14586 and asked for someone using GCC on Win32 to confirm that the code still worked.

Accelerating Method Dispatch

chromatic posted a link to thoughts on method dispatch by Piers Cawley and Avi Bryant. He wondered if it was similar to PIC. Andy Armstrong replied that the articles describe branch prediction for method dispatch, which he felt was different from PIC. Leopold Toetsch thought there were some similarities, and that further optimization was possible.

[TODO] fill Parrot_register_move() with code : new implementation

Karl Forner included a patch to revise Parrot_register_move() to address some bugs and improve speed. The algorithm was explained in detail. It was applied as r14621. Leopold Toetsch commented on the implementation.

HOWTO give options to parrot in tests

Karl Forner is working on [perl #40064]. He is wondering how he can run the script with options, and wanted to know if TEST_PROG_ARGS would be an appropriate choice. Leopold Toetsch suggested subclassing Parrot::Test.

Global Variables Hunting

Alberto Simões requested that anyone who found a global variable under IMCC/PIR parser add a 'HITME!' comment near it and alert him.

cur_namespace under imcc.y

Alberto Simões wanted to know if cur_namespace in imcc.y had the same meaning as the one in imc.h. He wanted to merge them.

Version PMC

Leopold Toetsch noted that GMP 4.1.1 segfaulted during multiplication. He corrected the problem by compiling and installing a new GMP, but he would like to create a diagnostic to warn about the bad GMP version.


the in Perl 6

Darren Duncan made the suggestion that be improved for Perl 6 rather than simply ported. He listed a few ways in which it could be improved. Mark Stosberg replied and mentioned some of the points he considered most important. These suggestions in particular received further discussion: removing HTML generation methods, renaming the module, and incorporating session management.

Trey Harris agreed with Mark's sentiment about excluding HTML methods from, but felt this could lead to limited Perl 6 adoption. Thomas Wittek suggested use perl5:CGI for legacy support and allowing to develop. Amir E. Aharoni was also in favor of the backwards-compatibility module, and an improved default. David Cantrell wondered if anyone was actually using HTML-generation. In Andy Dougherty's opinion, there are probably many people using it that way, because it features heavily in the documentation. Leon Timmermans admitted to using them a few times, and wanted a modern equivalent, but in a separate module. There were a number of other comments. The general gist seemed to be that HTML-generation functionality is used and should still be available, but optional.

The discussion of HTML methods led to Steffen Schwigon's observation that could use a name change to make it appear more modern. Darren Duncan and Juerd also disliked the current name. David Cantrell and Darren discussed whether 'CGI' implies an implementation or a standard interface.

In CGI Session management (was Re: the in Perl 6), Michael Snoyman suggested making session management easier, and perhaps integrating it. Yuval Kogman requested that session handling be left to a plugin, and offered to share what he had learned from redesigning the Catalyst session handling.

Trying to use Perl5 modules

Richard Hainsworth has been trying to discover how to use Perl 5 modules in Perl 6. He included some code which worked in Perl 5, and asked how he could use them in Pugs. Trey Harris replied that imports currently don't work, and showed a workaround. Audrey Tang answered that imports were implemented a few weeks ago, but implicit imports aren't supported yet.

Richard also wanted to know where .can is documented.

Google "Welcome to the home page for Perl 6" (Perl 6 Wiki)

Conrad Schneiker noticed that Google had indexed the Perl 6 Wiki but that it hasn't yet reached the top search results.


typo in HTTP::Server::Simple

Zack Hobson found a problem with the port number reported in startup by HTTP::Server::Simple in Pugs if the default port is used, and included a patch, which Carl Mäsak applied.


This summary was prepared using Mail::Summary::Tools, now available on CPAN.

If you appreciate Perl, consider contributing to the Perl Foundation to help support the development of Perl.

Yuval Kogman assisted with this summary.

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,


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