From: ts <decoux@...>
Date: 2002-12-15T00:59:12+09:00
Subject: Re: Is it wise to extend Matrix?

>>>>> "J" == Jim Freeze <jim@freeze.org> writes:

J> Sorry, but being new to delegators, can you show an example of "but must
J> return an object which is a delegator..."

 Here  what do DelegateClass in delegate.rb

def DelegateClass(superclass)
  klass = Class.new
  methods = superclass.instance_methods(true)
  methods -= ::Kernel.instance_methods
  methods |= ["to_s","to_a","inspect","==","=~","==="]
  klass.module_eval <<-EOS
  def initialize(obj)
    @obj = obj
  end
  EOS
  for method in methods
    klass.module_eval <<-EOS
        def #{method}(*args, &block)
          begin
            @obj.__send__(:#{method}, *args, &block)
          rescue
            $@[0,2] = nil
            raise
          end
        end
        EOS
      end
    return klass;
  end


 All wrapped function return the result of

     @obj.__send__(:#{method}, *args, &block)

 where @obj in your case is a Matrix Object

 When you write

   m = MyMatrix[[1,2],[3,4]]
   n = MyMatrix[[1,2],[3,4]]
   o = m + n

 ruby will call the method #+ for @obj which is a Matrix and fatally the
 result is a Matrix when you want an instance of MyMatrix


Guy Decoux