castaway has asked for the wisdom of the Perl Monks concerning the following question:

.. apparently doesn't work.. here's a bit of code I was attempting to use, but @args doesn't get set outside of the call to the coderef.. 
    $Commands{'who'} = [
                        {
        'pattern'   => '^who (.+)$',                              #'
        'mudindex'  => 1,
        'commandi2' => sub { @args = ($1, 'who'); print Dumper(\@args)
+;},
        'commandi3' => sub { @args = ('who-req', getUser(), $1); print
+ Dumper(\@rgs);},
        'syntax'    => 'who <mudname>' 
        },
                        {
        'pattern'   => '^who$',                                     #'
        'command' => sub { who_local($userid); },
        'syntax'    => 'who' 
        }];

....
    my @command = @{$Commands{$com}};
    my @args = ();
    foreach my $commands (@command)
    {
         debug("commands: " . Dumper($commands));
         ...

        if(my @res = $input =~ /$commands->{'pattern'}/)
        {       
            debug("results: " . Dumper(\@res));
            if($commands->{'mudindex'})
        {
                     ...

            $commands->{'commandi2'}->();
            debug("ARGS: " . Dumper(\@args));
            my $result = $i2->send($Users{$userid}{'user'}, @args);

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*goes off to think of another way to do it*

C.

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Re: Using $1,$2 etc in closures..
by chromatic (Archbishop) on Mar 07, 2003 at 21:23 UTC

    Since you declare @args as a lexical outside of the loop and the data structure before the loop, the closures aren't closed over the @args you think they are. :)

    I'd pass @res to your data structure, but I'm paranoid about passing backref variables directly. It bit me in Regex::English or Test::MockObject at least once.

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Re: Using $1,$2 etc in closures..
by castaway (Parson) on Mar 07, 2003 at 22:23 UTC
    Hmm.. silly me..
    Just changed it to: 
    'commandi2' => sub { return ($1, 'who');},

    [download]
    and
    @args = $commands->{'commandi2'}->();

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    .. Voila, no closures.. (Or it works, at least, which is the main thing..)

    C.

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Re: Using $1,$2 etc in closures..
by grantm (Parson) on Mar 07, 2003 at 22:14 UTC

    I think the key point here is that $1, $2, $3 etc are global variables. Referring to a global from within an anonymous sub doesn't make it a closure.

    The following code generates a closure since $x is a lexical in the scope enclosing the anonymous sub:

      sub make_closure {
    my $x = 1;
    my $closure = sub { 
      return $x++; 
    };
    return $closure;
  }

  my $cls = make_closure();
  print &$cls;
  print &$cls;
  print &$cls;

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      Regex match variables aren't actually global. They're... odd. But not global. (Neither are they lexical, though they're mostly lexical. Mostly)
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        Oh, well that clears that up then. Thanks :-)

        Whatever they are, I think we can all probably agree they're fairly transient in nature and if they contain anything you want then you ought to be saving it somewhere safe real quick.

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Re: Using $1,$2 etc in closures..
by zengargoyle (Deacon) on Mar 08, 2003 at 02:18 UTC

    i was poking around with some code in the recent image size pure perl thread and came up with some similar code.

    use strict;

my @test = (
        [ '^GIF8..(....)' => sub {
                return ( GIF => unpack("SS", $_[1]) );
                }],
        [ '^^\xFF\xD8.{4}JFIF' => sub { 
                return ( JPEG => unpack("nn", $1)) if ($_[0] =~ /\xFF\
+xC0...(...
.)/s);
                }],
        [ '^\x89PNG\x0d\x0a\x1a\x0a' => sub {
                return ( PNG => unpack("NN", $1)) if ($_[0] =~ /IHDR(.
+{8})/s);
                }],
        [ 'BM.{16}(.{8})' => sub {
                return ( BMP => unpack("LL", $_[1]) );
                }],
);

sub x_image_size {
        return unless $_[0];
        foreach my $test (@test) {
                my @arg;
                return ($test->[1]($_[0], @arg)) if (@arg = $_[0] =~ /
+$test->[0]/s);
        }
}

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Re: Using $1,$2 etc in closures..
by Elian (Parson) on Mar 25, 2003 at 17:40 UTC
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