From: Robert Klemme <bob.news@...>
Date: 2005-05-03T15:04:30+09:00
Subject: Re: collections with values of fixed classes/lengths


"Eric Mahurin" <eric_mahurin@yahoo.com> schrieb im Newsbeitrag 
news:20050502203538.19806.qmail@web41106.mail.yahoo.com...

>> > That would be great.  What do you mean by "fixed size
>> type"?
>> > Does that mean you couldn't use this class to make a
>> > homogeneous array of strings, arrays, or hashes?
>>
>> Exactly.  Because for that to work you need info about each
>> instance
>> stored there.  And then you have Array.
>
> But, you still wouldn't have to store the class info for each
> element.  I'm not sure of the underlying Ruby object data
> structure, but at a minimum, it should get rid of a pointer (to
> the class) per element.  I think you'd have to implement this
> in C to do it right.

I don't think it's worth the effort.  That must be a very special case where 
you need huge collections of inhomogenous data where you want to squeeze out 
every byte.   I can't think of an application of this.  Plus, it'll be error 
prone and very inefficient.


<snip/>

> Thanks for the implementation.  Another option for implementing
> this in Ruby may be to use Marshal dump/load and remove/prepend
> the class information.  You would at least be able to remove
> the  class of the top-level object.
>
> I still like having to specify a default object (instead of
> just a class) for specifying what types of objects are in the
> collection because:
>
> * when the collection expands with empty elements you need to
> put something there.  nil won't work because it is a different
> class (NilClass).  You need a default object to put in
> otherwise what comes out is undefined (may give garbage or
> exceptions).

Just add a method to the traits that returns this object (or can create a 
new object).

> * you can handle more general classes because you have access
> to the "instance_variables" (or "members" for Struct), etc.
> You can also contemplate using Marshal - for completely
> fixed-length objects.

What would you gain by this?  Every instance of a single class can have a 
complete different set of instance variables.

> * you can handle deep objects by using the default object as a
> template for how deep the homogeneity runs.

This sounds too theoretical for me.

> * this default/template object can also provide a mechanism for
> specifying fixed-length strings/array/integers.

I'm sorry, I don't get you here.  What do you mean by "specifying"?

Regards

    robert