From: hal9000@...
Date: 2000-12-23T03:40:02+09:00
Subject: [ruby-talk:7974] Re: Naming of "defined?"

See below...

In article <3A4382EE.3C10B51E@nycap.rr.com>,
  craig duncan <duncan@nycap.rr.com> wrote:
> Didn't i read that '?' at the end of a method name indicated a boolean
> return value?
>
> defined? returns the symbol type, not a boolean.
>
> Therfore, this sort of confusion:
>
> craig@duncan:/usr/home/craig/ruby$ cat t.rb
> #!/usr/bin/ruby
>
> def i
>   p "defining i as method"
> end
> p defined? i
>
> i = 0 if not defined? i
> p defined? i
>
> craig@duncan:/usr/home/craig/ruby$ t.rb
> "method"
> "local-variable"
>

Disclaimer: I don't have a Ruby interpreter handy at the moment.

What if i really is undefined? Doesn't it return false or nil?

And really, that is adequate for a Boolean, there being no Boolean
type as such in Ruby. The fact that it returns different meaningful
values for truth could be viewed as just a bonus.

Still, it's nice to know that you can distinguish in this way between
a method name and a local variable... I've just never seen anyone do it
as far as I can recall.

Hal

--
Hal Fulton


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