[14489] | 1 | package base;
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| 2 |
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| 3 | use strict 'vars';
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| 4 | use vars qw($VERSION);
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| 5 | $VERSION = '2.07';
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| 6 |
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| 7 | # constant.pm is slow
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| 8 | sub SUCCESS () { 1 }
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| 9 |
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| 10 | sub PUBLIC () { 2**0 }
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| 11 | sub PRIVATE () { 2**1 }
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| 12 | sub INHERITED () { 2**2 }
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| 13 | sub PROTECTED () { 2**3 }
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| 14 |
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| 15 |
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| 16 | my $Fattr = \%fields::attr;
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| 17 |
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| 18 | sub has_fields {
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| 19 | my($base) = shift;
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| 20 | my $fglob = ${"$base\::"}{FIELDS};
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| 21 | return( ($fglob && *$fglob{HASH}) ? 1 : 0 );
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| 22 | }
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| 23 |
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| 24 | sub has_version {
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| 25 | my($base) = shift;
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| 26 | my $vglob = ${$base.'::'}{VERSION};
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| 27 | return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
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| 28 | }
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| 29 |
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| 30 | sub has_attr {
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| 31 | my($proto) = shift;
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| 32 | my($class) = ref $proto || $proto;
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| 33 | return exists $Fattr->{$class};
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| 34 | }
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| 35 |
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| 36 | sub get_attr {
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| 37 | $Fattr->{$_[0]} = [1] unless $Fattr->{$_[0]};
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| 38 | return $Fattr->{$_[0]};
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| 39 | }
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| 40 |
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| 41 | if ($] < 5.009) {
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| 42 | *get_fields = sub {
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| 43 | # Shut up a possible typo warning.
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| 44 | () = \%{$_[0].'::FIELDS'};
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| 45 | my $f = \%{$_[0].'::FIELDS'};
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| 46 |
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| 47 | # should be centralized in fields? perhaps
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| 48 | # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' }
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| 49 | # is used here anyway, it doesn't matter.
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| 50 | bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');
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| 51 |
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| 52 | return $f;
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| 53 | }
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| 54 | }
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| 55 | else {
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| 56 | *get_fields = sub {
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| 57 | # Shut up a possible typo warning.
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| 58 | () = \%{$_[0].'::FIELDS'};
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| 59 | return \%{$_[0].'::FIELDS'};
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| 60 | }
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| 61 | }
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| 62 |
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| 63 | sub import {
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| 64 | my $class = shift;
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| 65 |
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| 66 | return SUCCESS unless @_;
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| 67 |
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| 68 | # List of base classes from which we will inherit %FIELDS.
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| 69 | my $fields_base;
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| 70 |
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| 71 | my $inheritor = caller(0);
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| 72 |
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| 73 | foreach my $base (@_) {
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| 74 | next if $inheritor->isa($base);
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| 75 |
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| 76 | if (has_version($base)) {
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| 77 | ${$base.'::VERSION'} = '-1, set by base.pm'
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| 78 | unless defined ${$base.'::VERSION'};
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| 79 | }
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| 80 | else {
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| 81 | local $SIG{__DIE__};
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| 82 | eval "require $base";
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| 83 | # Only ignore "Can't locate" errors from our eval require.
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| 84 | # Other fatal errors (syntax etc) must be reported.
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| 85 | die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
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| 86 | unless (%{"$base\::"}) {
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| 87 | require Carp;
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| 88 | Carp::croak(<<ERROR);
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| 89 | Base class package "$base" is empty.
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| 90 | (Perhaps you need to 'use' the module which defines that package first.)
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| 91 | ERROR
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| 92 |
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| 93 | }
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| 94 | ${$base.'::VERSION'} = "-1, set by base.pm"
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| 95 | unless defined ${$base.'::VERSION'};
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| 96 | }
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| 97 | push @{"$inheritor\::ISA"}, $base;
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| 98 |
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| 99 | if ( has_fields($base) || has_attr($base) ) {
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| 100 | # No multiple fields inheritence *suck*
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| 101 | if ($fields_base) {
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| 102 | require Carp;
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| 103 | Carp::croak("Can't multiply inherit %FIELDS");
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| 104 | } else {
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| 105 | $fields_base = $base;
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| 106 | }
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| 107 | }
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| 108 | }
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| 109 |
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| 110 | if( defined $fields_base ) {
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| 111 | inherit_fields($inheritor, $fields_base);
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| 112 | }
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| 113 | }
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| 114 |
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| 115 |
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| 116 | sub inherit_fields {
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| 117 | my($derived, $base) = @_;
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| 118 |
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| 119 | return SUCCESS unless $base;
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| 120 |
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| 121 | my $battr = get_attr($base);
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| 122 | my $dattr = get_attr($derived);
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| 123 | my $dfields = get_fields($derived);
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| 124 | my $bfields = get_fields($base);
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| 125 |
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| 126 | $dattr->[0] = @$battr;
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| 127 |
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| 128 | if( keys %$dfields ) {
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| 129 | warn "$derived is inheriting from $base but already has its own ".
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| 130 | "fields!\n".
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| 131 | "This will cause problems.\n".
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| 132 | "Be sure you use base BEFORE declaring fields\n";
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| 133 | }
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| 134 |
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| 135 | # Iterate through the base's fields adding all the non-private
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| 136 | # ones to the derived class. Hang on to the original attribute
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| 137 | # (Public, Private, etc...) and add Inherited.
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| 138 | # This is all too complicated to do efficiently with add_fields().
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| 139 | while (my($k,$v) = each %$bfields) {
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| 140 | my $fno;
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| 141 | if ($fno = $dfields->{$k} and $fno != $v) {
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| 142 | require Carp;
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| 143 | Carp::croak ("Inherited %FIELDS can't override existing %FIELDS");
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| 144 | }
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| 145 |
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| 146 | if( $battr->[$v] & PRIVATE ) {
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| 147 | $dattr->[$v] = PRIVATE | INHERITED;
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| 148 | }
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| 149 | else {
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| 150 | $dattr->[$v] = INHERITED | $battr->[$v];
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| 151 | $dfields->{$k} = $v;
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| 152 | }
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| 153 | }
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| 154 |
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| 155 | foreach my $idx (1..$#{$battr}) {
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| 156 | next if defined $dattr->[$idx];
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| 157 | $dattr->[$idx] = $battr->[$idx] & INHERITED;
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| 158 | }
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| 159 | }
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| 160 |
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| 161 |
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| 162 | 1;
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| 163 |
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| 164 | __END__
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| 165 |
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| 166 | =head1 NAME
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| 167 |
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| 168 | base - Establish IS-A relationship with base classes at compile time
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| 169 |
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| 170 | =head1 SYNOPSIS
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| 171 |
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| 172 | package Baz;
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| 173 | use base qw(Foo Bar);
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| 174 |
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| 175 | =head1 DESCRIPTION
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| 176 |
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| 177 | Allows you to both load one or more modules, while setting up inheritance from
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| 178 | those modules at the same time. Roughly similar in effect to
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| 179 |
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| 180 | package Baz;
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| 181 | BEGIN {
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| 182 | require Foo;
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| 183 | require Bar;
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| 184 | push @ISA, qw(Foo Bar);
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| 185 | }
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| 186 |
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| 187 | If any of the listed modules are not loaded yet, I<base> silently attempts to
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| 188 | C<require> them (and silently continues if the C<require> failed). Whether to
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| 189 | C<require> a base class module is determined by the absence of a global variable
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| 190 | $VERSION in the base package. If $VERSION is not detected even after loading
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| 191 | it, <base> will define $VERSION in the base package, setting it to the string
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| 192 | C<-1, set by base.pm>.
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| 193 |
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| 194 | Will also initialize the fields if one of the base classes has it.
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| 195 | Multiple inheritence of fields is B<NOT> supported, if two or more
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| 196 | base classes each have inheritable fields the 'base' pragma will
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| 197 | croak. See L<fields>, L<public> and L<protected> for a description of
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| 198 | this feature.
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| 199 |
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| 200 | =head1 DIAGNOSTICS
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| 201 |
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| 202 | =over 4
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| 203 |
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| 204 | =item Base class package "%s" is empty.
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| 205 |
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| 206 | base.pm was unable to require the base package, because it was not
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| 207 | found in your path.
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| 208 |
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| 209 | =back
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| 210 |
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| 211 | =head1 HISTORY
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| 212 |
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| 213 | This module was introduced with Perl 5.004_04.
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| 214 |
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| 215 |
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| 216 | =head1 CAVEATS
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| 217 |
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| 218 | Due to the limitations of the implementation, you must use
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| 219 | base I<before> you declare any of your own fields.
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| 220 |
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| 221 |
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| 222 | =head1 SEE ALSO
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| 223 |
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| 224 | L<fields>
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| 225 |
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| 226 | =cut
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