=head1 VERSION
Maintainer: Michael Schwern <[EMAIL PROTECTED]>
Date: 16 September 2000
Mailing List: perl6-language
Number: ?
Version: 1
Status: Developing (Last Call)
Reply-To: perl6-language @perl.org
This and other RFCs are available on the web at
http://dev.perl.org/rfc/
=head1 TITLE
Pseudo-hashes must die!
=head1 VERSION
Maintainer: Michael Schwern <[EMAIL PROTECTED]>
Date: 16 September 2000
Mailing List: perl6-language @perl.org
Number: 241
Version: 1
Status: Developing (Last Call)
=head1 ABSTRACT
Pseudo-hashes and the associated fields pragma shoule be removed from
Perl 6.
=head1 DESCRIPTION
There are numerous insuperable problems with pseudo-hashes, as
detailed in "Object Oriented Perl" and "Programming Perl, Ed. 3".
They are a noble experiment that many feel has failed. They should be
removed.
Pseudo-hashes have existed since at least May 28th, 1997 when they were
added as patch #2 to what would eventually become 5.004_50. Two
years, three months and 20 days later they're still considered
experimental, incomplete and loaded with caveats.
Doesn't play well with multiple inheritance
Muddles the behavior of typed variables
Requires significant extra documentation and complication of
hash operations.
Inconsistencies between typed and untyped access.
Pseudo-hashes, unless used very carefully, often turn out slower
than hashes.
Pseudo-hashes were added to solve three problems: restrict keyspace,
reduce memory usage and increase speed of hashes. There are many RFCs
which address these issues with less caveats.
There has been some discussion on p5p regarding the removal of
pseudo-hashes (and other experimental features) should their
adolescence take too long. Two major revisions of experimentation was
given as a rough limit to declaring an experiment as a failure.
The extensive development time, continued experimental nature, caveats
and availability of better proposals lead to one conclusion:
B<PSEUDO-HASHES MUST DIE>
=head1 MIGRATION
Considerable. Most would be solved by a clever rejigging of the
fields pragma to revert to simple hashes or other Perl 6 features. A
100% perfect conversion will not be achieved without an inorderinate
amount of work. Since pseudohashes were an experimental feature, a
less-than-perfect migration is acceptable. You pays your money and
you takes your chances. (As a fairly extensive user of pseudohashes,
I'm willing to take the hit.)
=head1 IMPLEMENTATION
Very simple, don't implement it. :) In Perl 5 terms, avhv functions
removed from av.c, pseudo-hash code removed from pp.c, pp_hot.c,
doop.c, mg.c, embed.pl etc.... and pseudo-hash documentation caveats
removed from perlref and perlfunc.
=head1 REFERENCES
Discussion of experation of experimental features.
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2000-01/msg00017.html
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2000-01/msg00255.html
RFCs which supplant pseudohash functionality.
RFC 188 - Objects : Private keys and methods
RFC 200 - Objects: Revamp tie to support extensibility (Massive tie changes)
RFC 163 - Automatic accessors for hash-based objects
RFC 124 - Sort order for any hash
RFC 122 - types and structures
etc...
http://us.imdb.com/Title?0165929
http://us.imdb.com/Title?0102691
http://us.imdb.com/Title?0094077
http://us.imdb.com/Title?0054474
