[ruby-talk:5117] Re: Types and ===

From: [e-mail]
Subject: [ruby-talk:5114] Types and ===
Date: Tue, 26 Sep 2000 08:40:01 +0900

> Reason with me: Normally when x == y, x === y is also true (I'm
> not saying the converse!!). But I have found a case where it isn't.
> I can see there may be others.)
> 
> See the fragment below, and its output.
> 
> classify1 and classify2 don't do the same thing. The first fails;
> the second works. classify3 also works.

ahm... I might be missing something.  You said '*Normally* when x ==
y, ...', and also you said you know '==' is not '===' but assuming
Module#=== is equal to Module#== ?

try this:

o = Object.new
p (Object === o)
p (Object == o)

"Object === o" is equal to "o.is_a? Object".  that makes easier to
write case statement.

def classify4(arg)
  case arg
    when String
      print "  arg is a string\n"
    when Array
      print "  arg is an array\n"
    when Hash
      print "  arg is a hash\n"
    else
      print "  arg is unknown\n"
  end
end
--
         yashi