From: Mathieu Bouchard <matju@...>
Date: 2001-01-31T13:27:55+09:00
Subject: [ruby-talk:10157] Re: ArrayMixin 0.2


On Wed, 31 Jan 2001, David Alan Black wrote:
> On Wed, 31 Jan 2001, Mathieu Bouchard wrote:
> > Second "release" of ArrayMixin 0.2, a future equivalent to Perl's TIEARRAY
> > system.
> Can anyone help me out with an example or problem where Ruby (as it
> currently is) does not already allow us to do what we might do with
> Perl tie, with about the same amount of work?  (Perl: define STORE,
> Ruby: (re)define #[]=, etc.)  I seem to be absolutely unable to see
> it.

In Perl you don't need to redefine the array slice. You don't need to
implement the complete semantics of what appears to be a store. When you
do:

	$blah[1] = 2

what is being done is really:

	tied(@blah)->STORE(1,2)
	tied(@blah)->FETCH(1)

In Ruby, #[]= has more features yet than Perl's assignments, and Perl
already abstracts out its assignment operations, so I told myself: why
not in Ruby?

ArrayMixin is designed to minimise the effort on the implementor of an
Array-like class, by taking that concept of Perl (tie) and refining it.

If you are willing to reimplement the complete functionality #[]= and #[]
by yourself every time, would you please send me a sample implementation
that I could include in ArrayMixin. Thank you.

----------------8<----------------cut-here----------------8<----------------
package Foo;

sub TIEARRAY {
	my ($class) = @_;
	my $self = bless {}, $class;
	return $self;}

sub STORE {
	my ($self,$i,$v) = @_;
	print "at: $i put: $v.\n";}

sub FETCH {
	return 42;}

1;
----------------8<----------------cut-here----------------8<----------------

Perl> tie @blah, 'Foo'
Foo=HASH(0x80c2990)

Perl> $blah[1] = 2
at: 1 put: 2.
42

Perl> @blah[1..3] = (1,4,9)
at: 1 put: 1.
at: 2 put: 4.
at: 3 put: 9.
3

----------------8<----------------cut-here----------------8<----------------

matju