From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-04-13T01:18:03+09:00
Subject: Re: Why Object#class Is Inconsistent in "==" and "case"?

In the previous example by Guy Decoux,

    module MyModule
      ....
      case obj
      when MyClass    # line NNN
        ....
      end
    end

in Ruby, line NNN evaluates to "MyClass === obj" and not "obj ===
MyClass"?  Is there any documentation on this and what is the
rationale?  Again, does this conform to the Priciple of Least Surprise or
just some additional Ruby tricks that I have to memorize?  (Last time it
was Array.new (n, Hash.new) creates an array of n references of the single
hash object, which is not useful in practice.)

Why can't we make "MyClass === obj" and "obj === MyClass" to behave in the
same way so that we don't have to deal with this extra peculiarity?  (We
can simply define Object#== is true for identical objects and Object#===
is true for identical object classes, just like the kind_of? method.)

Again, it seems that by using == and if-elsif-else construct everything is
natural; but once we use the case statement, there are too many
nitty-gritty details that may make the case statement really
dangerous.  Based on this, probably case statement should be degraded to
second class Ruby construct and the if-elsif-else as the first class as
there may be arbitrary objects that randomly redefine the === method.

Regards,

Bill
==========================================================================
Dave Thomas <Dave@pragmaticprogrammer.com> wrote:
> You're using Module#===, not Object#=== in your example.
> Dave