From: "trans.  (T. Onoma)" <transami@...>
Date: 2005-01-14T00:07:49+09:00
Subject: Re: Duck Typing as Pattern Matching

I haven't read the entire thread so forgive me if I'm rehashing....

On Thursday 13 January 2005 09:51 am, itsme213 wrote:
| "ts" <decoux@moulon.inra.fr> wrote in message
|
| > p txn.respond_to?(:create_modify)
| > p txn.create_modify
|
| Oh oh, even more Ruby experts join the chorus ? :-)
|
| My claim is this: If you redefine #method_missing so your object handles
| x.foo as the caller would expect, then you _should_ define
| x.respond_to?(:foo) to return true. I do not claim that Ruby should
| prohibit code that does not do this.

I wonder if method missing would be better if these two "tiers" were built in 
to it. This would require dual "blocks" so I'm not sure how to notate it but:

  def method_missing(meth, *args)
  upon meth == :create_modify
    # do whatever
  upon ...
    # ...
  end

Then #respond_to? can utilize the "upon" block to determine responses 
correctly.

| I am interested in your thoughts on this claim.
|
| p.s. I know it is possible to redefine #send so that x.send :foo works, but
| x.foo does not. I think this a practice to be actively discouraged. But
| let's leave that out for now.

Redefining #send is a very bad idea. IMHO That's one of those methods I think 
should be off limits and return an error if you try to redefine it.

T.