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=head1 TITLE
Ensuring Perl's object-oriented future
=head1 VERSION
Maintainer: John Siracusa <[EMAIL PROTECTED]>
Date: Aug 16 2000
Version: 1
Mailing List: [EMAIL PROTECTED]
Number: 126
=head1 ABSTRACT
Object-oriented features were added to Perl with version 5, and in many
ways still appear somewhat "tacked on", with perhaps undue respect
for the Old Ways of Perl 4. We have a chance to change things for the
better with Perl 6.
Perl 6 should allow object-oriented programming with the same ease and
efficiency that it allows procedural programming.
=head1 DESCRIPTION
There are many RFC's already on objects and classes in Perl. I'd like
to tie all the disparate implementation-specific RFC's together with a
unifying direction: ensuring that people who like to program with
object-oriented Perl get the native language features they need to do so
cleanly and efficiently.
There are a lot of stumbling blocks to efficient object-oriented
programming in Perl 5. It's great that the implementation allows so
much flexibility, and some very clever things can be done with all that
rope (see Damian Conway's wonderful book), but to quote Larry Wall:
"Although the Perl Slogan is There's More Than One Way to Do It,
I hesitate to make 10 ways to do something."
Guess how many ways there are to make classes and objects and methods in
Perl. The bottom line is that we're really using hashes and arrays and
scalars and the concept of "blessing" to dandy up Perl 4 into an
object-oriented language.
This wouldn't bother me so much if it wasn't also incredibly inefficient
relative to procedural Perl. Of course object-oriented design will
always have more overhead, but it shouldn't be I<that> much more.
To put it another way, no one should ever be tempted to do this:
$obj->{'attribute'}
for efficiency reasons inside a tight loop or what have you. (And no,
the solution is not to "use C when you need efficiency." I shouldn't
need to use portable assembler to access an object attribute
efficiently.) Whatever the syntax turns out to be, simple things like
object attribute accessors should not only be faster than doing this
in Perl 5:
$obj->attribute
they should even be faster than the naughty, encapsulation-destroying,
implementation-revealing hash-lookup above. As for performance relative
to procedural Perl code, I'm thinking something along the lines of
Objective C's efficiency vs. plain C. Objective C is nearly as dynamic
as Perl and doesn't give up too much to plain C in terms of execution
speed. (And as a superset of a procedural language, it's a good analogy
for Perl's o-o implementation.)
I don't think pseudohashes and such go far enough. I don't want "faster
hash-based objects" or just "faster method dispatch", I want real,
honest to goodness classes with attributes and methods and such that are
distinct, both in syntax and implementation, from other Perl data
structures like hashes and arrays.
Yes, this may force Perl 6 to make decisions about exactly which
object-oriented features will be "natively" supported in Perl. But this
is not all bad. After all, someone somewhere decided how the procedural
stuff should work; there aren't 50 ways to return a value from a
function, for example. Decisions have to be made and syntax has to be
created. There will still be plenty of Ways to Do It, in my opinion.
The old procedural model should remain, of course. I'm not advocating a
Java-like transformation into object-oriented bondage. And I'm not
saying that every one of Perl's internal functions and operators should
be replaced with object-oriented variants. All I'm asking for is a
better world for object-oriented Perl programmers.
I think it's important to focus on this so it doesn't get lost in all
the discussion of new letters to tack onto "m/.../sogie" and new syntax
for range operators and such ;) And I think it's something that
everyone can agree on, since there's a lot of benefit to be had, and no
down-side that I can see.
Let's make Perl 6 an awesome language for object-oriented development.
=head1 IMPLEMENTATION
That's up to the other relevant RFC's.
=head1 REFERENCES
Damian Conway's "Object Oriented Perl"
RFC 95: Object Classes
RFC 73: All Perl core functions should return objects
RFC 80: Exception objects and classes for builtins
All the other present and future RFC's dealing with object-oriented
Perl 6 features.
