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Ovid (2709)

Ovid
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Stuff with the Perl Foundation. A couple of patches in the Perl core. A few CPAN modules. That about sums it up.

Journal of Ovid (2709)

Saturday April 21, 2007
02:36 PM

Perl6::Caller

[ #33062 ]

Update 1: Oops. Seems that Christian Lembark has the permission rights to the caller namespace. Working around that now.

Update 2: Turns out that he has a 'package caller' declaration in his FindBin::libs module. Thus, he owns that namespace.

I've just uploaded Perl6::Caller. If you read this and it's not on the CPAN, just wait a few hours. Feedback and bug reports gratefully accepted. I had to do a couple of weird things to get it to work and I decided that, at least for the first release, to not allow optional overriding of CORE::GLOBAL::caller. Relevant docs:

NAME
    Perl6::Caller - OO "caller()" interface

VERSION
    Version 0.01

SYNOPSIS
     use Perl6::Caller;

     my $sub         = caller->subroutine;
     my $line_number = caller->line;
     my $is_require  = caller(3)->is_require;

EXPORT
"caller"
     # standard usage
     print "In ",           caller->subroutine,
           " called from ", caller->file,
           " line ",        caller->line;

     # get a caller object
     my $caller = caller;
     my $caller = caller();   # same thing

     # get a caller object for a different stack from
     my $caller = caller(2);  # two stack frames up
     print $caller->package;  # prints the package name

     # enjoy the original flavor
     my @caller = caller;     # original caller behavior
     print $caller[0],        # prints the package name

DESCRIPTION
    This module is experimental. It's also alpha. Bug reports and patches
    welcome.

    By default, this module exports the "caller" function. This
    automatically returns a new "caller" object. An optional argument
    specifies how many stack frames back to skip, just like the
    "CORE::caller" function. This lets you do things like this:

     print "In ",           caller->subroutine,
           " called from ", caller->file,
           " line ",        caller->line;

    If you do not wish the "caller" function imported, specify an empty
    import list and instantiate a new "Perl6::Caller" object.

     use Perl6::Caller ();
     my $caller = Perl6::Caller->new;
     print $caller->line;

    Note: if the results from the module seem strange, please read
    perldoc -s caller carefully. It has stranger behavior than you might be
    aware.

METHODS
    The following methods are available on the "caller" object. They return
    the same values as documented in perldoc -f caller.

    There are no "hints" and "bitmask" methods because those are documented
    as for internal use only.

    *   "package"

    *   "filename"

    *   "line"

    *   "subroutine"

    *   "hasargs"

    *   "wantarray"

    *   "evaltext"

    *   "is_require"

    Note that each of these values will report correctly for when the caller
    object was created. For example, the following will probably print
    different line numbers:

     print caller->line;
     foo();
     sub foo {
        print caller->line;
     }

    However, the following will print the *same* line numbers:

     my $caller = Perl6::Caller->new;   # everything is relative to here
     print $caller->line;
     foo($caller);
     sub foo {
        my $caller = shift;
        print $caller->line;
     }

CAVEATS
    Most of the time, this package should *just work* and not interfere with
    anything else.

    *   $hints, $bitmask

        'hints' and 'bitmask' are not available. They are documented to
        be for internal use only and should not be relied upon. Further, the
        bitmask caused strange test failures, so I opted not to include
        them.

    *   "caller" package

        To make this work, we actually use the 'caller' package in addition
        to the "Perl6::Caller" package.

    *   Subclassing

        Don't.

    *   Perl 6

        I'm not entirely comfortable with the namespace. The Perl 6 caller
        actually does considerably more, but for me to have a hope of
        working that in, I need proper introspection and I don't have that.
        Thus, I've settled for simply having a caller object.

    *   *CORE::GLOBAL::caller

        I didn't implement this, though I was tempted. It turns out to be a
        bit tricky in spots and I'm very concerned about globally overriding
        behavior. I might change my mind in the future if there's enough
        demand.

    *   Overloading

        In string context, this returns the package name. This is to support
        the original "caller" behavior.

    *   List Context

        In list context, we simply default to the original behavior of
        "CORE::caller". However, this *always* assumes we've called caller
        with an argument. Calling "caller" and caller(0) are identical with
        this module. It's difficult to avoid since the stack frame changes.

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  • ...for what exactly do you need the 'caller' namespace?
    --
    Ordinary morality is for ordinary people. -- Aleister Crowley
    • I don't. In the first (unreleased) version, I was having some serious issues with caller->line being called as a class method at times, but as caller()->line at other times (things got very strange which is part of why CORE::GLOBAL::caller has not been overridden). I can't quite work out how I got there, but I separated the namespace to make this work. Now I've fixed that and version 0.04 should be uploaded soon. Thanks for the prodding.