The Sidhekin wrote:
> The packages you declare "internal" are not what you think they are.
> Observe:
>
> sidhekin@bluebird[07:57:50]~$ perl -le '$t{ __PACKAGE__ }++; print
keys %t;'
> __PACKAGE__
I noticed that in the debugger, but didn't know if it was a literal
string or a shortcut similar to Data::Dumper...
> sidhekin@bluebird[07:57:52]~$ perl -le '$t{ +__PACKAGE__ }++; print keys
> %t;'
> main
> sidhekin@bluebird[07:57:53]~$ perl -le '$t{ (__PACKAGE__) }++; print keys
Thank you. The second form is per RTFM -- I didn't pay enough attention
and missed the parentheses. The fixed demonstration program follows.
I recently tripped over hash key context (or whatever it's call) when I
attempted to use constants for hash keys. Now I can add something else
to the shopping list:
2011-01-17 13:04:07 dpchrist@p43400e ~/sandbox
$ nl -b a hash-key-context.pl
1 #!/usr/bin/perl
2 use strict;
3 use warnings;
4 use Data::Dumper;
5 use constant KEY => 1;
6 my %hash;
7 $hash{ KEY } = __LINE__;
8 $hash{ KEY() } = __LINE__;
9 $hash{ __PACKAGE__ } = __LINE__;
10 $hash{ (__PACKAGE__) } = __LINE__;
11 print Data::Dumper->Dump([\%hash], [qw(*hash)]);
2011-01-17 13:04:16 dpchrist@p43400e ~/sandbox
$ perl hash-key-context.pl
%hash = (
'KEY' => '7',
'1' => '8',
'__PACKAGE__' => '9',
'main' => '10'
);
Camel book 3 "Scalar and List Context" (pp. 69-70) and "Hashes" (pp.
76-78) aren't much help. Where is hash key context explained?
> %t;'
> main
> sidhekin@bluebird[07:57:54]~$
>
> Careful with those barewords, now. ;-)
I can't find __PACKAGE__ in the Camel book 3 index (?). STFW I found it
in the online Perl Cookbook, where it's called a symbol:
http://docstore.mik.ua/orelly/perl/cookbook/ch12_06.htm
The online Camel book calls it a special literal token:
http://docstore.mik.ua/orelly/perl4/prog/ch02_06.htm
David
2011-01-17 12:19:55 dpchrist@p43400e ~/sandbox
$ nl -b a carp-internal2.pl
1 #!/usr/bin/perl
2
3 package Foo;
4 use Carp;
5 $Carp::Internal{ (__PACKAGE__) }++;
6 sub myconfess {
7 eval {
8 Carp::confess @_;
9 };
10 print $@, "\n";
11 }
12
13 package Bar;
14 use Carp;
15 sub myconfess {
16 local $Carp::CarpLevel = 2;
17 eval {
18 Carp::confess @_;
19 };
20 print $@, "\n";
21 }
22
23 package Baz;
24 use Carp;
25 $Carp::CarpInternal{ (__PACKAGE__) }++;
26 sub myconfess {
27 eval {
28 Carp::confess @_;
29 };
30 print $@, "\n";
31 }
32
33 package main;
34 sub run {
35 Foo::myconfess('goodbye, cruel world!');
36 Bar::myconfess('goodbye, cruel world!');
37 Baz::myconfess('goodbye, cruel world!');
38 }
39 run();
2011-01-17 12:20:04 dpchrist@p43400e ~/sandbox
$ perl carp-internal2.pl
goodbye, cruel world! at carp-internal2.pl line 35
main::run() called at carp-internal2.pl line 39
goodbye, cruel world! at carp-internal2.pl line 36
main::run() called at carp-internal2.pl line 39
goodbye, cruel world! at carp-internal2.pl line 37
main::run() called at carp-internal2.pl line 39
