From: Sigurd <cu9ypd@...>
Date: 2012-03-07T05:08:50+09:00
Subject: Re: Getting the class of an object.

defined? is a INSN RTL, there for it's not "defined" in the ruby script lexical scope. 
To be clearer - it's Ruby keyword, not a method or whatever.

On Mar 6, 2012, at 9:55 PM, Sam Duncan wrote:

> On 07/03/12 08:48, Ralph Shnelvar wrote:
>> Sam,
>> 
>> Tuesday, March 6, 2012, 12:09:45 PM, you wrote:
>> 
>> SD>  On 07/03/12 07:15, Robert Klemme wrote:
>>>> You do not want the class but rather the kind of "foo".  "local
>>>> variable" is not a class.  You can do
>>>> 
>>>> irb(main):032:0>   class Bogey<   Dance
>>>> irb(main):033:1>   def bar
>>>> irb(main):034:2>   a=0
>>>> irb(main):035:2>   printf "foo ->   %p\n", defined?(foo)
>>>> irb(main):036:2>   printf "a ->   %p\n", defined?(a)
>>>> irb(main):037:2>   printf "none ->   %p\n", defined?(none)
>>>> irb(main):038:2>   end
>>>> irb(main):039:1>   end
>>>> =>   nil
>>>> irb(main):040:0>   Bogey.new.bar
>>>> foo ->   "method"
>>>> a ->   "local-variable"
>>>> none ->   nil
>>>> =>   nil
>> SD>  Great answer. I'm pretty new to Ruby and assumed that defined? returned
>> SD>  a boolean. That'll learn me for not reading the manual.
>> 
>> SD>  Sam
>> 
>> Indeed, it is a great answer. Thanks Robert!
>> 
>> Now where in online documentation can I find where "defined?" is documented?
>> 
>> I see it explained on page 137 of the Pickaxe book but is there more formal documentation online?
>> 
>> Also ... I find it interesting that I get a syntax error when I do
>>   defined? defined?
> 
> Yeah, that is odd.
> 
> 1.9.2p290 :001 > defined? defined?
> SyntaxError: (irb):1: syntax error, unexpected $end
>    from ~/.rvm/rubies/ruby-1.9.2-p290/bin/irb:16:in `<main>'
> 1.9.2p290 :002 > defined?(defined?)
> SyntaxError: (irb):2: syntax error, unexpected ')'
>    from ~/.rvm/rubies/ruby-1.9.2-p290/bin/irb:16:in `<main>'
> 1.9.2p290 :003 > defined? :defined?
> => "expression"
> 
> Sam
> 
>