From: matz@... (Yukihiro Matsumoto)
Date: 2000-12-23T12:30:54+09:00
Subject: [ruby-talk:7986] Re: Naming of "defined?"

Hi,

In message "[ruby-talk:7961] Naming of "defined?""
    on 00/12/23, craig duncan <duncan@nycap.rr.com> writes:

|Didn't i read that '?' at the end of a method name indicated a boolean
|return value?

The '?' methods are methods designed to be used as predicates, not
methods which CAN be used as predicate.  They return either

  (a) true or false
  (b) non-false informative value or nil

`defined?' falls into (b).

In addition, as a rare exception, Thread#alive? returns true for
unterminated threads, false for normally terminated threads, and nil
for threads terminated by exceptions.

							matz.