From: ts <decoux@...>
Date: 2001-01-23T19:43:35+09:00
Subject: [ruby-talk:9761] Re: 101 Misconceptions About Dynamic Languages

>>>>> "C" == Christoph Rippel <crippel@primenet.com> writes:

C> class A
C>   N = 13  # this is the crucial part

 The problem here is that N is resolved at compile time

C>   def initialize n
C>       @rep = n % N
C>   end
C>   def + (r)
C>        (@rep + rep.r) % N
                  ^^^^^
                  r.rep

  no ?

C>   end
C>   attr_reader :rep
C> ...
C> end


C> The import thing is that the type information is attached to the object ...

C> a1 =  A.new 11
C> a2 =  B.new 11
C> b1 =  C.new 10  # definitely want A.id == C.id
C> b2 =  B.new 11  # is nor hard but is not natively supported

C> than the internal representation of

C> a1 + b1 and a2 + b2

C> won't be equal.

 Probably this not what you want (I know nothing about math :-))

pigeon% cat b.rb
#!/usr/bin/ruby
class  Ring
   @@class = {}
   def Ring.mod_ZZ(n)
      return @@class[n] if @@class.key? n
      a = Class.new(self)
      a.module_eval "N = #{n}"
      @@class[n] = a
      a
   end
  def initialize( n)
     @rep = n % self.class::N
  end
  def + (r)
       (@rep + r.rep) % self.class::N
  end
  attr_reader :rep
end
 
 
A  = Ring.mod_ZZ 13
B  = Ring.mod_ZZ 23
C = Ring.mod_ZZ 13
a1 =  A.new 11
a2 =  B.new 11
b1 =  C.new 10
p A.id == C.id
b2 =  B.new 11
p a1 + b1
p a2 + b2
pigeon%
 
pigeon% b.rb
true
8
22
pigeon% 


Guy Decoux