From: furufuru@... (Ryo Furue)
Date: 2001-09-28T14:48:36+09:00
Subject: [ruby-talk:21795] Help: how to (re)define the unary minus?

Hi there,

I'm wondering how one should (re)define the unary minus operator for a
class.  The following fails:

   class Complex
      attr_accessor :re, :im
      def initialize(re, im)
         @re = re; @im = im
      end
      def -() # unary???
         Complex.new(-@re, -@im)
      end
      def to_s
         "(" + @re.to_s + "," + @im.to_s + ")"
      end
   end

   a = Complex.new(3.14, 1.73)
   puts -a

with

  ./try.rb:17: undefined method `-@' for #<Complex:0xe7f60>
(NameError)

I checked the pickaxe book but coudn't find a relevent discussion. 
Note that what I want to create is not a complex class; I've used it
as an obvious example.

Cheers,
Ryo