This Week on perl5-porters (5-11 August 2002)

This Week on perl5-porters (5-11 August 2002)
    This week, the report comes a little bit earlier than expected, due to a
    short schedule. However it will not be shorter -- this week was rich in
    events and in discussions about the future of Perl 5.

  Experiments with the defined-or operator
    Hugo applied the patch by Brent Dax that introduces the "//", "err" and
    "//=" operators (defined-or, low-priority defined-or, and defined-or
    assignment). H.Merijn Brand seriously thinks *about building 5.8.0 with
    it and put it production*. However this new syntax introduces minor
    incompatibilities, so Hugo wants to make it available in the future
    through a new pragma "use perl6ish".

    On this same topic, Chris Reinhardt noticed that "shift // 0" is a
    syntax error. In fact, the parser, seeing the tokens "shift //", can't
    decide between "shift(//)" (the regexp) and "shift // ..." (the
    operator). I suggested that, although difficult to solve in the general
    case (e.g. with "split"), this can be made to work for the "shift"
    operator and most of others. (That's what we call DWIMmery.)

    This problem doesn't occur in Perl 6, where "//" is not a valid pattern.

        http://groups.google.com/groups?threadm=Pine.GSO.4.44.0208091457550.19151-100000%40quartz.bos.dyndns.org

  Improving $^H and %^H
    To implement new pragmas (such as "perl6ish") or to make the existing
    "sort" pragma work with lexical scopes, it's necessary to have a
    mechanism to retrieve the existing set of pragmas in any scope during
    the compilation. This mechanism is currently provided by the $^H and
    "%^H" special variables. But "%^H" has at least one problem : it's not
    propagated to "eval """ statements. This has to be fixed.

    It would also be handy to access, after the compilation phase, the set
    of pragmas a particular op has been compiled with. For example, this
    could be useful for the "B::" modules, or for anything that manipulates
    the optree. For the moment, this works only with the "integer", "strict
    'refs'", "locale" and "bytes" pragmas (you can for example get them
    through the 9th value returned by caller(N)).

        http://groups.google.com/groups?threadm=200208052352.g75NqGj05578%40crypt.compulink.co.uk

        http://groups.google.com/groups?threadm=3D511373.8050706%40hexaflux.com

  v-strings bite again
    Abigail reported a (known) bug (#16010) : the fat comma doesn't quote
    v-strings. Hence

        perl -we 'print v65 => "\n"'

    prints "A\n" (at least on ASCII platforms). John Peacock (who knows the
    v-strings inner odds and ends, for having worked on them) explained the
    root of the problem : the parser immediately converts "v65" into a
    string "A" and there is currently no way to distinguish them after
    compilation.

    John then supplied quickly a patch to add magic to v-string scalars, so
    a copy of the initial string representation is preserved. With this
    information in place, it will be probably possible to correct a large
    part of the annoyances caused by v-strings.

        http://groups.google.com/groups?threadm=3D4FF061.7030802%40rowman.com

        http://groups.google.com/groups?threadm=3D530D01.9010000%40rowman.com

  Plans for Perl 5.10
    Arthur Bergman posted a list of ideas for Perl 5.10. Shortly : replace
    magic by parrot-like PMCs, provide a strict typing pragma, decrease
    general memory overhead, improve threads, and improve the introspection
    mechanisms of Perl (e.g. the "B::" modules). This triggerred quite a bit
    of comments -- especially about the proposed replacement of the magic
    system, used to implement all Perl magic variables, and other things
    too.

    Benjamin Goldberg then dropped some additionnal ideas of his own : for
    example, allow $/ to be a regexp. Nicholas Clark added that more tests
    can't hurt.

        http://groups.google.com/groups?threadm=F4096C04-AAAE-11D6-AF7A-003065D64CBE%40contiller.se

  Pseudo-hashes
    Michael G Schwern submitted a complete patch to remove pseudo-hashes.
    With his patch, places that were using pseudo-hashes (as fields.pm) use
    the new (as of 5.8.0) restricted hashes. He added that some future
    improvements can be made on the top of his patch. He made also some
    benchmarking and noticed (quite surprisingly) no performance improvement
    ; some more digging is needed on this, as he previously estimated an
    average 15% speedup on hash operations.

        http://groups.google.com/groups?threadm=20020806200510.GC31473%40ool-18b93024.dyn.optonline.net
        http://groups.google.com/groups?threadm=20020806215439.GA26308%40ool-18b93024.dyn.optonline.net

    Johannes Plass, a pseudo-hash user, wondered if the compile-time
    checking features of the current pseudo-hashes will be preserved with
    the new implementation of fields.pm and base.pm.

        http://groups.google.com/groups?threadm=3D558057.7010003%40web.de

  In brief
    Dave Mitchell added a new debugging option, "-Dv", aimed at making the
    other debugging options more verbose. He supplied also a verbose version
    of "-Ds" (to trace stack contents).

        http://groups.google.com/groups?threadm=20020805005533.B26111%40fdgroup.com

    Robin Berjon pointed the P5P readers at an entry in Leon Brocard's
    use.perl journal, about securing CPAN. Only Andreas Koenig replied, but
    I feel that this idea is finding its way in the porters' minds.

        http://groups.google.com/groups?threadm=02080502111402.12618%40morgaine

    Tim Bunce suggested that porting XS core modules to "Inline::C" might
    make them more easily portable to Perl 6. Brian Ingerson and Dan
    Sugalski disagreed, unless someone defines a compatibility API on top of
    XS and Parrot.

    The perl5-changes mailing list (where commits to the Perl 5 source
    repository are sent) seems to be allergic to Hugo.

    A couple of bug reports about gcc 3.1 not being able to build perl 5.6.1
    were sent. This is a known problem with gcc 3.1. H.Merijn Brand
    suggested to make a patch available on CPAN.

    John P. Linderman found that "/.{,3}/" is not the same pattern as
    "/.{0,3}/" : the lower bound is not optional. Mark-Jason Dominus says :
    *It turns out it has been this way since Perl 1.*

    Vadim Konovalov found a bug in seek/tell when the ":crlf" PerlIO layer
    is used, and found also the root cause of it (Bug #15986). This was
    fixed by Nick Ing-Simmons.

    Hugo released the first development snapshot. The smoke tests are up
    again.

  About this summary
    This summary brought to you by Rafael Garcia-Suarez, just before taking
    his annual vacation. Thanks to Elizabeth Mattijsen, who will take it
    over for the next two weeks. It's also available via a mailing list,
    which subscription address is [email protected].