From: "David A. Black" <dblack@...>
Date: 2004-11-15T09:00:18+09:00
Subject: Re: Why can't I get an array range, like [3, 4], on a Struct?

Hi --

On Mon, 15 Nov 2004, Sam Roberts wrote:

> I just noticed I can't do:
> 
>   x = Struct.new(...
>   puts x[3, 4]
>   
> I'm doing this, instead, which works fine:
> 
>   x = Struct.new(...
>   puts x.to_a[3, 4]
> 
> I guess it is because [] is not part of Enumerable, but why isn't []
> defined by Enumerable? Is it because random access is so inefficient
> when implemented with an iterator, for large collections, anyhow?
> 
> Maybe I answered my own question. :-)
> 
> I vaguely remember some discussion of some modules that would allow a
> class that supported to_str mix in support for all the other String
> methods, and something similar for Array/to_a, as well.
> 
> I'd like to mix a little bit more of Array into Struct!

You can do that (just write a module and extend your Structs), though
in general I think Structs are more hash-like than array-like.  If
there's a #[] method, I wouldn't expect it to be restricted to
integers.  (Is the order of #to_a for Structs even guaranteed?)

(Tangential question:

How does one refer to the methods one defines on a Struct, or for that
matter its other instance methods?  The usual ClassName#method_name
thing doesn't work :-)


David

-- 
David A. Black
dblack@wobblini.net