110 lines
2.9 KiB
Perl
110 lines
2.9 KiB
Perl
# ==================================================================
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# Gossamer Threads Module Library - http://gossamer-threads.com/
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#
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# bases
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# Author: Scott Beck
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# CVS Info :
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# $Id: bases.pm,v 1.9 2004/01/13 01:35:15 jagerman Exp $
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#
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# Copyright (c) 2004 Gossamer Threads Inc. All Rights Reserved.
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# ==================================================================
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package bases;
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use strict 'subs', 'vars';
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sub import {
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my $class = shift;
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my $pkg = caller;
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my $hsh = {@_};
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my @indices = map { $_[$_ * 2] } 0 .. $#_ * 0.5;
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foreach my $base (@indices) {
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next if $pkg->isa($base);
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push @{"$pkg\::ISA"}, $base;
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my $args = '';
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if (my $ref = ref $hsh->{$base}) {
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require GT::Dumper;
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if ($ref eq 'ARRAY') {
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$args = '(@{' . GT::Dumper->dump_structure($hsh->{$base}) . '})';
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}
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else {
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$args = '(' . GT::Dumper->dump_structure($hsh->{$base}) . ')';
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}
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}
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elsif (defined $hsh->{$base}) {
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$args = $hsh->{$base} eq '' ? '()' : "qw($hsh->{$base})";
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}
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my $dcl = qq|
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package $pkg;
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use $base $args;
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|;
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eval $dcl;
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die "$@: $dcl" if $@ && $@ !~ /^Can't locate .*? at \(eval /;
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unless (defined %{"$base\::"}) {
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require Carp;
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Carp::croak(
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qq|Base class package "$base" is empty.
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String:
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$dcl
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\t(Perhaps you need to 'use' the module which defines that package first.)|
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);
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}
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}
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}
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1;
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__END__
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=head1 NAME
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base - Establish IS-A relationship with base class at compile time.
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=head1 SYNOPSIS
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package Baz;
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use bases
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Foo => ':all',
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Bar => ''
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Bat => undef;
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=head1 DESCRIPTION
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Roughly similar in effect to
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package Baz;
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use Foo qw(:all);
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use Bar();
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use Bat;
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BEGIN { @ISA = qw(Foo Bar Bat) }
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This is very similar to C<base> pragma except %FIELDS is not
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supported and you are able to pass parameters to import on the
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module that is used in this way.
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If the value specified is undef, the module being used import method
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will be called if it exists. If the value is an empty string, import
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will not be called.
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When strict 'vars' is in scope I<bases> also let you assign to @ISA
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without having to declare @ISA with the 'vars' pragma first.
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If any of the base classes are not loaded yet, I<bases> silently
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C<use>s them. Whether to C<use> a base class package is
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determined by the absence of a global $VERSION in the base package.
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If $VERSION is not detected even after loading it, <base> will
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define $VERSION in the base package, setting it to the string
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C<-1, set by bases.pm>.
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=head1 COPYRIGHT
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Copyright (c) 2004 Gossamer Threads Inc. All Rights Reserved.
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http://www.gossamer-threads.com/
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=head1 VERSION
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Revision: $Id: bases.pm,v 1.9 2004/01/13 01:35:15 jagerman Exp $
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=cut
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