It was Friday, December 12, 2003 when Luke Palmer took the soap box, saying:
: So I'm seeing a lot of inconsistent OO-vocabulary around here, and it
: makes things pretty hard to understand.
Awesome. I've taken your original, plus comments so far and created
perlvocab.pod. Lets give it a couple go-rounds and it can be stored
in CVS for safe keeping (and maintaining). Send me diffs if you like.
Document below sig.
Casey West
--
Usenet is like Tetris for people who still remember how to read.
-- Button from the Computer Museum, Boston, MA
=pod
=head1 NAME
perlvocab - Perl Vocabulary and Glossary
=head1 SYNOPSIS
This document authoritatively defines many potentially ambiguous terms in Perl.
=head1 DESCRIPTION
=head2 Object Oriented Terminology
=over 4
=item attribute
A concrete data member of a class. Declared with C<has>.
=item property
A run-time, out-of-band sticky note to be placed on a single object,
applied with with C<but>.
A property is a simple kind of role that supplies a single attribute.
The type of a property is identical to its role name. Roles can have
subtypes that function as enums when the subtypes are constrained to a
single value. You can use one of these subtypes without specifically
implying the role name. So saying
$bar but Red
might give you a value with the property Color. You can write the corresponding
boolean test using the smart match operator:
$bar ~~ Red
and it (smartly) picks out the Color property to compare with, provided
it's unambiguous. You can use that syntax to compare against any
subtype or junction of subtypes:
$bar ~~ Redish&Whiteish # pinkish
=item trait
A compile-time sticky note to be placed on a wide variety of things.
Used with C<is>.
=item role
A collection of methods and/or attributes to be incorporated into a class sans
inheritance (and maybe some other stuff, too). A role can be applied to a class
at compile time via C<does>, or to an object at run time via C<but>.
So for example:
class Dog
does Boolean # role
is extended # trait
is Mammal # base class
{
has $.tail; # attribute
has @.legs; # attribute
}
my $fido = Dog.new
but false; # property
In this example, C<Mammal> is a base class, which is an overloaded use of C<is>.
Though,
upon A12 release, we'll probably find out that it's not overloaded but
instead, elegantly unified, somehow.
=head1 AUTHOR
Luke Palmer, Original Document
Contributions by Larry Wall, and Jonathan Scott Duff
Compilation by Casey West
=cut
