From: Daniel Brockman <daniel@...>
Date: 2005-07-16T09:36:16+09:00
Subject: Re: difference?

Devin Mullins <twifkak@comcast.net> writes:

> Daniel Brockman wrote:
>
>>Interestingly, `is?' works really well for adjectival arguments:
>>   foo.is? Enumerable      foo.is? Observable
>>It's actually not that bad for substantival arguments either:
>>   foo.is? String          foo.is? Array
>>  
>>
> Indeed, I like the look of that. I imagine, however, he added the _a
> because he didn't want to crowd the method namespace (I assume the
> same reason he changed id to object_id).

I don't think `is?' crowds it any more than `is_a?'.  Rather, I guess
he used the latter because `is-a' was a well-established term.

>>(Note that `kind_of?' works well in all these cases:
>>   foo.kind_of? Enumerable       foo.kind_of? Observable
>>   foo.kind_of? String           foo.kind_of? Array)
>>
> I can see that. I guess it's just that I'm not used to thinking of
> instances as "kinds."

Fair enough.  Indeed, when functional programming geeks talk about
type systems they will often distinguish between `types' and `kinds'.

> Also "kind of" comes off sounding like "approximately," which is
> kind of weird.

Granted, but that's actually not a completely unsuitable connotation.
The Collaborative International Dictionary of English has the
following to say about the term ``kind of'':

   A kind of, something belonging to the class of; something
      like to; -- said loosely or slightingly.

Keep in mind that `kind_of?', unlike `instance_of?', does not check
strict class--instance relationships, but allows subtype instances.

> I'm obviously too closed-minded for Ruby. :)

I don't know... you seem pretty open-minded to me. :-)

-- 
Daniel Brockman <daniel@brockman.se>

    So really, we all have to ask ourselves:
    Am I waiting for RMS to do this?   --TTN.